Semiconductor device and method of forming a vertical interconnect structure for 3-D FO-WLCSP

ABSTRACT

A semiconductor device has a temporary carrier. A semiconductor die is oriented with an active surface toward, and mounted to, the temporary carrier. An encapsulant is deposited with a first surface over the temporary carrier and a second surface, opposite the first surface, is deposited over a backside of the semiconductor die. The temporary carrier is removed. A portion of the encapsulant in a periphery of the semiconductor die is removed to form an opening in the first surface of the encapsulant. An interconnect structure is formed over the active surface of the semiconductor die and extends into the opening in the encapsulant layer. A via is formed and extends from the second surface of the encapsulant to the opening. A first bump is formed in the via and electrically connects to the interconnect structure.

CLAIM TO DOMESTIC PRIORITY

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 12/572,590, filed Oct. 2, 2009, which is a divisionof U.S. patent application Ser. No. 12/333,977, now U.S. Pat. No.7,642,128, filed Dec. 12, 2008, and further claims the benefit ofProvisional Application No. 61/441,561, filed Feb. 10, 2011 andProvisional Application No. 61/444,914, filed Feb. 21, 2011. The presentapplication claims priority to the above applications pursuant to 35U.S.C. §120.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and,more particularly, to a semiconductor device having a verticalinterconnect structure for three-dimensional (3-D) fan-out wafer levelchip scale packages (FO-WLCSPs).

BACKGROUND OF THE INVENTION

Semiconductor devices are commonly found in modern electronic products.Semiconductor devices vary in the number and density of electricalcomponents. Discrete semiconductor devices generally contain one type ofelectrical component, e.g., light emitting diode (LED), small signaltransistor, resistor, capacitor, inductor, and power metal oxidesemiconductor field effect transistor (MOSFET). Integrated semiconductordevices typically contain hundreds to millions of electrical components.Examples of integrated semiconductor devices include microcontrollers,microprocessors, charged-coupled devices (CCDs), solar cells, anddigital micro-mirror devices (DMDs).

Semiconductor devices perform a wide range of functions such as signalprocessing, high-speed calculations, transmitting and receivingelectromagnetic signals, controlling electronic devices, transformingsunlight to electricity, and creating visual projections for televisiondisplays. Semiconductor devices are found in the fields ofentertainment, communications, power conversion, networks, computers,and consumer products. Semiconductor devices are also found in militaryapplications, aviation, automotive, industrial controllers, and officeequipment.

Semiconductor devices exploit the electrical properties of semiconductormaterials. The atomic structure of semiconductor material allows itselectrical conductivity to be manipulated by the application of anelectric field or base current or through the process of doping. Dopingintroduces impurities into the semiconductor material to manipulate andcontrol the conductivity of the semiconductor device.

A semiconductor device contains active and passive electricalstructures. Active structures, including bipolar and field effecttransistors, control the flow of electrical current. By varying levelsof doping and application of an electric field or base current, thetransistor either promotes or restricts the flow of electrical current.Passive structures, including resistors, capacitors, and inductors,create a relationship between voltage and current necessary to perform avariety of electrical functions. The passive and active structures areelectrically connected to form circuits, which enable the semiconductordevice to perform high-speed calculations and other useful functions.

Semiconductor devices are generally manufactured using two complexmanufacturing processes, i.e., front-end manufacturing, and back-endmanufacturing, each involving potentially hundreds of steps. Front-endmanufacturing involves the formation of a plurality of die on thesurface of a semiconductor wafer. Each semiconductor die is typicallyidentical and contains circuits formed by electrically connecting activeand passive components. Back-end manufacturing involves singulatingindividual semiconductor die from the finished wafer and packaging thedie to provide structural support and environmental isolation. The term“semiconductor die” as used herein refers to both the singular andplural form of the words, and accordingly, can refer to both a singlesemiconductor device and multiple semiconductor devices.

One goal of semiconductor manufacturing is to produce smallersemiconductor devices. Smaller devices typically consume less power,have higher performance, and can be produced more efficiently. Inaddition, smaller semiconductor devices have a smaller footprint, whichis desirable for smaller end products. A smaller semiconductor die sizecan be achieved by improvements in the front-end process resulting insemiconductor die with smaller, higher density active and passivecomponents. Back-end processes may result in semiconductor devicepackages with a smaller footprint by improvements in electricalinterconnection and packaging materials.

Another goal of semiconductor manufacturing is to produce semiconductordevices with adequate heat dissipation. High frequency semiconductordevices generally generate more heat. Without effective heatdissipation, the generated heat can reduce performance, decreasereliability, and reduce the useful lifetime of the semiconductor device.

The electrical interconnection between a FO-WLCSP containingsemiconductor devices on multiple levels (3-D device integration) andexternal devices can be accomplished with conductive through siliconvias (TSV) or through hole vias (THV). In most TSVs and THVs, thesidewalls and bottom-side of the via are conformally plated withconductive materials to enhance adhesion. The TSVs and THVs are thenfilled with another conductive material, for example, by copperdeposition through an electroplating process. The TSV and THV formationtypically involves considerable time for the via filling, which reducesthe unit-per-hour (UPH) production schedule. The equipment need forelectroplating, e.g., plating bath, and sidewall passivation increasesmanufacturing cost. In addition, voids may be formed within the vias,which causes defects and reduces reliability of the device. TSV and THVcan be a slow and costly approach to make vertical electricalinterconnections in semiconductor packages. These interconnect schemesalso have problems with semiconductor die placement accuracy, warpagecontrol before and after removal of the carrier, and process costmanagement.

The electrical interconnection between 3-D FO-WLCSPs and externaldevices, in addition to including TSVs and THVs, further includesredistribution layers (RDLs). RDLs serve as intermediate layers forelectrical interconnect within a package including electricalinterconnect with package I/O pads which provide electrical connectionfrom semiconductor die within 3-D FO-WLCSP to points external to 3-DFO-WLCSPs. RDLs can be formed over both a front side and a backside of asemiconductor die within a 3-D FO-WLCSP. However, the formation ofmultiple RDLs including over a front side and backside of asemiconductor die can be a slow and costly approach for makingelectrical interconnection for 3-D FO-WLCSPs and can result in higherfabrication costs.

SUMMARY OF THE INVENTION

A need exists to provide an interconnect structure for 3-D semiconductordevices. Accordingly, in one embodiment, the present invention is amethod of making a semiconductor device including the steps of providinga temporary carrier, mounting a semiconductor die with an active surfaceoriented toward the temporary carrier, and depositing an encapsulantwith a first surface over the temporary carrier and a second surfaceopposite the first surface. The second surface is over a backside of thesemiconductor die. The method further includes the steps of removing thetemporary carrier, removing a portion of the encapsulant in a peripheryof the semiconductor die to form an opening in the first surface of theencapsulant, forming an interconnect structure over the active surfaceof the semiconductor die and extending into the opening, forming a viafrom the second surface of the encapsulant to the opening, and forming afirst bump in the via that electrically connects to the interconnectstructure.

In another embodiment, the present invention is a method of making asemiconductor device including the steps of providing a semiconductordie with an active surface, depositing an encapsulant in a periphery ofthe semiconductor die with a first surface and a second surface oppositethe first surface and over a backside of the semiconductor die, removinga portion of the encapsulant from the first surface to form an opening,forming an interconnect structure over the active surface of thesemiconductor die and extending into the opening, forming a via from thesecond surface of the encapsulant to the opening, and depositing aconductive material in the via that electrically connects to theinterconnect structure.

In another embodiment, the present invention is a method of making asemiconductor device including the steps of providing a semiconductordie with an active surface, depositing an encapsulant in a periphery ofthe semiconductor die with a first surface and a second surface oppositethe first surface, depositing a conductive material in the periphery ofthe semiconductor die extending from the first surface to the secondsurface of the encapsulant, and forming an interconnect structure overthe active surface of the semiconductor die and electrically connectedto the conductive material.

In another embodiment, the present invention is a semiconductor deviceincluding a semiconductor die with an active surface. An encapsulant isdeposited in a periphery of the semiconductor die with a first surfaceand a second surface opposite the first surface. An interconnectstructure is formed over the active surface of the semiconductor die. Aconductive via extends from the second surface of the encapsulant to theinterconnect structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a printed circuit board (PCB) with different types ofpackages mounted to its surface;

FIGS. 2 a-2 c illustrate further detail of the representativesemiconductor packages mounted to the PCB;

FIGS. 3 a-3 c illustrate a semiconductor wafer with a plurality ofsemiconductor die separated by saw streets;

FIGS. 4 a-4 k illustrate a process of forming a vertical interconnectstructure for FO-WLCSP;

FIGS. 5 a-5 b illustrate the FO-WLCSP with vertical interconnectstructure having conductive pillars;

FIG. 6 illustrates an alternate embodiment of the FO-WLCSP with verticalinterconnect structure;

FIG. 7 illustrates the multi-layer UBM for the vertical interconnectstructure of the FO-WLCSP;

FIG. 8 illustrates an alternate embodiment of the FO-WLCSP with verticalinterconnect structure having conductive pillars and bumps;

FIGS. 9 a-9 c illustrate the FO-WLCSP with vertical interconnectstructure having RDL under the conductive pillars;

FIGS. 10 a-10 b illustrate another process of forming a verticalinterconnect structure for 3-D FO-WLCSP;

FIG. 11 illustrates the FO-WLCSP with vertical interconnect structurehaving encapsulant over the semiconductor die;

FIG. 12 illustrates the FO-WLCSP with another vertical interconnectstructure having encapsulant over the semiconductor die;

FIGS. 13 a-13 x illustrate another process of forming a verticalinterconnect structure for 3-D FO-WLCSP;

FIGS. 14 a-14 d illustrate a process of mounting a bumped semiconductordevice over a 3-D FO-WLCSP with vertical interconnect structure;

FIGS. 15 a-15 d illustrate another process of forming a verticalinterconnect structure for a 3-D FO-WLCSP;

FIGS. 16 a-16 d illustrate another process of forming a verticalinterconnect structure for a 3-D FO-WLCSP;

FIG. 17 illustrates another embodiment of the FO-WLCSP with a verticalinterconnect structure;

FIGS. 18 a-18 b illustrate an alternate embodiment of the FO-WLCSP witha vertical interconnect structure having conductive columns;

FIGS. 19 a-19 b illustrate another embodiment of a 3-D FO-WLCSP havingconductive vias;

FIGS. 20 a-20 b illustrate a 3-D FO-WLCSP having encapsulant over thesemiconductor die;

FIGS. 21 a-21 c illustrate 3-D FO-WLCSPs having stepped encapsulant;

FIGS. 22 a-22 c illustrate another embodiment of a 3-D FO-WLCSPincluding a heat sink or shielding layer;

FIG. 23 illustrates 3-D FO-WLCSPs having a crack stop layer;

FIGS. 24 a-24 b illustrate a 3-D FO-WLCSP including a horizontallyexpanded interconnect structure; and

FIGS. 25 a-25 b illustrate another embodiment of a 3-D FO-WLCSPincluding a horizontally expanded interconnect structure.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is described in one or more embodiments in thefollowing description with reference to the figures, in which likenumerals represent the same or similar elements. While the invention isdescribed in terms of the best mode for achieving the invention'sobjectives, it will be appreciated by those skilled in the art that itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims and their equivalents as supported by the followingdisclosure and drawings.

Semiconductor devices are generally manufactured using two complexmanufacturing processes: front-end manufacturing and back-endmanufacturing. Front-end manufacturing involves the formation of aplurality of die on the surface of a semiconductor wafer. Each die onthe wafer contains active and passive electrical components, which areelectrically connected to form functional electrical circuits. Activeelectrical components, such as transistors and diodes, have the abilityto control the flow of electrical current. Passive electricalcomponents, such as capacitors, inductors, resistors, and transformers,create a relationship between voltage and current necessary to performelectrical circuit functions.

Passive and active components are formed over the surface of thesemiconductor wafer by a series of process steps including doping,deposition, photolithography, etching, and planarization. Dopingintroduces impurities into the semiconductor material by techniques suchas ion implantation or thermal diffusion. The doping process modifiesthe electrical conductivity of semiconductor material in active devices,transforming the semiconductor material into an insulator, conductor, ordynamically changing the semiconductor material conductivity in responseto an electric field or base current. Transistors contain regions ofvarying types and degrees of doping arranged as necessary to enable thetransistor to promote or restrict the flow of electrical current uponthe application of the electric field or base current.

Active and passive components are formed by layers of materials withdifferent electrical properties. The layers can be formed by a varietyof deposition techniques determined in part by the type of materialbeing deposited. For example, thin film deposition can involve chemicalvapor deposition (CVD), physical vapor deposition (PVD), electrolyticplating, and electroless plating processes. Each layer is generallypatterned to form portions of active components, passive components, orelectrical connections between components.

The layers can be patterned using photolithography, which involves thedeposition of light sensitive material, e.g., photoresist, over thelayer to be patterned. A pattern is transferred from a photomask to thephotoresist using light. In one embodiment, the portion of thephotoresist pattern subjected to light is removed using a solvent,exposing portions of the underlying layer to be patterned. In anotherembodiment, the portion of the photoresist pattern not subjected tolight, the negative photoresist, is removed using a solvent, exposingportions of the underlying layer to be patterned. The remainder of thephotoresist is removed, leaving behind a patterned layer. Alternatively,some types of materials are patterned by directly depositing thematerial into the areas or voids formed by a previous deposition/etchprocess using techniques such as electroless and electrolytic plating.

Depositing a thin film of material over an existing pattern canexaggerate the underlying pattern and create a non-uniformly flatsurface. A uniformly flat surface is required to produce smaller andmore densely packed active and passive components. Planarization can beused to remove material from the surface of the wafer and produce auniformly flat surface. Planarization involves polishing the surface ofthe wafer with a polishing pad. An abrasive material and corrosivechemical are added to the surface of the wafer during polishing. Thecombined mechanical action of the abrasive and corrosive action of thechemical removes any irregular topography, resulting in a uniformly flatsurface.

Back-end manufacturing refers to cutting or singulating the finishedwafer into the individual semiconductor die and then packaging thesemiconductor die for structural support and environmental isolation. Tosingulate the semiconductor die, the wafer is scored and broken alongnon-functional regions of the wafer called saw streets or scribes. Thewafer is singulated using a laser cutting tool or saw blade. Aftersingulation, the individual semiconductor die are mounted to a packagesubstrate that includes pins or contact pads for interconnection withother system components. Contact pads formed over the semiconductor dieare then connected to contact pads within the package. The electricalconnections can be made with solder bumps, stud bumps, conductive paste,or bond wire. An encapsulant or other molding material is deposited overthe package to provide physical support and electrical isolation. Thefinished package is then inserted into an electrical system and thefunctionality of the semiconductor device is made available to the othersystem components.

FIG. 1 illustrates electronic device 10 having a chip carrier substrateor PCB 12 with a plurality of semiconductor packages mounted on itssurface. Electronic device 10 can have one type of semiconductorpackage, or multiple types of semiconductor packages, depending on theapplication. The different types of semiconductor packages are shown inFIG. 1 for purposes of illustration.

Electronic device 10 can be a stand-alone system that uses thesemiconductor packages to perform one or more electrical functions.Alternatively, electronic device 10 can be a subcomponent of a largersystem. For example, electronic device 10 can be part of a cellularphone, personal digital assistant (PDA), digital video camera (DVC), orother electronic communication device. Alternatively, electronic device10 can be a graphics card, network interface card, or other signalprocessing card that can be inserted into a computer. The semiconductorpackage can include microprocessors, memories, application specificintegrated circuits (ASICs), logic circuits, analog circuits, radiofrequency (RF) circuits, discrete devices, or other semiconductor die orelectrical components. Miniaturization and weight reduction areessential for these products to be accepted by the market. The distancebetween semiconductor devices must be decreased to achieve higherdensity.

In FIG. 1, PCB 12 provides a general substrate for structural supportand electrical interconnect of the semiconductor packages mounted on thePCB. Conductive signal traces 14 are formed on a surface or withinlayers of PCB 12 using evaporation, electrolytic plating, electrolessplating, screen printing, or other suitable metal deposition process.Signal traces 14 provide for electrical communication between each ofthe semiconductor packages, mounted components, and other externalsystem components. Traces 14 also provide power and ground connectionsto each of the semiconductor packages.

In some embodiments, a semiconductor device has two packaging levels.First level packaging is a technique for mechanically and electricallyattaching the semiconductor die to an intermediate carrier. Second levelpackaging involves mechanically and electrically attaching theintermediate carrier to the PCB. In other embodiments, a semiconductordevice may only have the first level packaging where the semiconductordie is mechanically and electrically mounted directly to the PCB.

For the purpose of illustration, several types of first level packaging,including bond wire package 16 and flip chip 18, are shown on PCB 12.Additionally, several types of second level packaging, including ballgrid array (BGA) 20, bump chip carrier (BCC) 22, dual in-line package(DIP) 24, land grid array (LGA) 26, multi-chip module (MCM) 28, quadflat non-leaded package (QFN) 30, and quad flat package 32, are shownmounted on PCB 12. Depending upon the system requirements, anycombination of semiconductor packages, configured with any combinationof first and second level packaging styles, as well as other electroniccomponents, can be connected to PCB 12. In some embodiments, electronicdevice 10 includes a single attached semiconductor package, while otherembodiments call for multiple interconnected packages. By combining oneor more semiconductor packages over a single substrate, manufacturerscan incorporate pre-made components into electronic devices and systems.Because the semiconductor packages include sophisticated functionality,electronic devices can be manufactured using less expensive componentsand a streamlined manufacturing process. The resulting devices are lesslikely to fail and less expensive to manufacture resulting in lowercosts for consumers.

FIGS. 2 a-2 c show exemplary semiconductor packages. FIG. 2 aillustrates further detail of DIP 24 mounted on PCB 12. Semiconductordie 34 includes an active region containing analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed within the die and are electricallyinterconnected according to the electrical design of the die. Forexample, the circuit can include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements formedwithin the active region of semiconductor die 34. Contact pads 36 areone or more layers of conductive material, such as aluminum (Al), copper(Cu), tin (Sn), nickel (Ni), gold (Au), or silver (Ag), and areelectrically connected to the circuit elements formed withinsemiconductor die 34. During assembly of DIP 24, semiconductor die 34 ismounted to an intermediate carrier 38 using a gold-silicon eutecticlayer or adhesive material such as thermal epoxy or epoxy resin. Thepackage body includes an insulative packaging material such as polymeror ceramic. Conductor leads 40 and bond wires 42 provide electricalinterconnect between semiconductor die 34 and PCB 12. Encapsulant 44 isdeposited over the package for environmental protection by preventingmoisture and particles from entering the package and contaminatingsemiconductor die 34 or bond wires 42.

FIG. 2 b illustrates further detail of BCC 22 mounted on PCB 12.Semiconductor die 46 is mounted over carrier 48 using an underfill orepoxy-resin adhesive material 50. Bond wires 52 provide first levelpackaging interconnect between contact pads 54 and 56. Molding compoundor encapsulant 60 is deposited over semiconductor die 46 and bond wires52 to provide physical support and electrical isolation for the device.Contact pads 64 are formed over a surface of PCB 12 using a suitablemetal deposition process such as electrolytic plating or electrolessplating to prevent oxidation. Contact pads 64 are electrically connectedto one or more conductive signal traces 14 in PCB 12. Bumps 66 areformed between contact pads 56 of BCC 22 and contact pads 64 of PCB 12.

In FIG. 2 c, semiconductor die 18 is mounted face down to intermediatecarrier 76 with a flipchip style first level packaging. Active region 78of semiconductor die 18 contains analog or digital circuits implementedas active devices, passive devices, conductive layers, and dielectriclayers formed according to the electrical design of the die. Forexample, the circuit can include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements withinactive region 78. Semiconductor die 18 is electrically and mechanicallyconnected to carrier 76 through bumps 80.

BGA 20 is electrically and mechanically connected to PCB 12 with a BGAstyle second level packaging using bumps 82. Semiconductor die 18 iselectrically connected to conductive signal traces 14 in PCB 12 throughbumps 80, signal lines 84, and bumps 82. A molding compound orencapsulant 86 is deposited over semiconductor die 18 and carrier 76 toprovide physical support and electrical isolation for the device. Theflipchip semiconductor device provides a short electrical conductionpath from the active devices on semiconductor die 18 to conductiontracks on PCB 12 in order to reduce signal propagation distance, lowercapacitance, and improve overall circuit performance. In anotherembodiment, the semiconductor die 18 can be mechanically andelectrically connected directly to PCB 12 using flipchip style firstlevel packaging without intermediate carrier 76.

FIG. 3 a shows a semiconductor wafer 90 with a base substrate material92, such as silicon, germanium, gallium arsenide, indium phosphide, orsilicon carbide, for structural support. A plurality of semiconductordie or components 112 is formed on wafer 90 separated by a non-active,inter-die wafer area or saw street 94 as described above. Saw street 94provides cutting areas to singulate semiconductor wafer 90 intoindividual semiconductor die 112.

FIG. 3 b shows a cross-sectional view of a portion of semiconductorwafer 90. Each semiconductor die 112 has a back surface 96 and activesurface 97 containing analog or digital circuits implemented as activedevices, passive devices, conductive layers, and dielectric layersformed within the die and electrically interconnected according to theelectrical design and function of the die. For example, the circuit mayinclude one or more transistors, diodes, and other circuit elementsformed within active surface 97 to implement analog circuits or digitalcircuits, such as digital signal processor (DSP), ASIC, memory, or othersignal processing circuit. Semiconductor die 112 may also containintegrated passive devices (IPDs), such as inductors, capacitors, andresistors, for RF signal processing. In one embodiment, semiconductordie 112 is a flipchip type device.

An electrically conductive layer 98 is formed over active surface 97using PVD, CVD, electrolytic plating, electroless plating process, orother suitable metal deposition process. Conductive layer 98 can be oneor more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitable electricallyconductive material. Conductive layer 98 operates as contact padselectrically connected to the circuits on active surface 97. Contactpads 98 can be disposed side-by-side a first distance from the edge ofsemiconductor die 112, as shown in FIG. 3 b. Alternatively, contact pads98 can be offset in multiple rows such that a first row of contact padsis disposed a first distance from the edge of the die, and a second rowof contact pads alternating with the first row is disposed a seconddistance from the edge of the die.

An electrically conductive bump material is deposited over contact pads98 using an evaporation, electrolytic plating, electroless plating, balldrop, or screen printing process. The bump material can be Al, Sn, Ni,Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, with an optionalflux solution. For example, the bump material can be eutectic Sn/Pb,high-lead solder, or lead-free solder. The bump material is bonded tocontact pads 98 using a suitable attachment or bonding process. In oneembodiment, the bump material is reflowed by heating the material aboveits melting point to form balls or bumps 114. In some applications,bumps 114 are reflowed a second time to improve electrical contact tocontact pads 98. Bumps 114 can also be compression bonded to contactpads 98. Bumps 114 represent one type of interconnect structure that canbe formed over contact pads 98. The interconnect structure can also usestud bump, micro bump, or other electrical interconnect.

In FIG. 3 c, semiconductor wafer 90 is singulated through saw street 94using a saw blade or laser cutting tool 99 into individual semiconductordie 112.

FIGS. 4 a-4 k illustrate, in relation to FIGS. 1 and 2 a-2 c, a processof forming a vertical interconnect structure for 3-D FO-WLCSP. In FIG. 4a, a substrate or wafer 100 contains dummy or sacrificial base materialsuch as silicon (Si), polymer, polymer composite, metal, ceramic, glass,glass epoxy, beryllium oxide, or other suitable low-cost, rigid materialor bulk semiconductor material for structural support.

The interface layer 102 can be temporary bonding film or etch-stoplayer. The temporary bonding film can be either heat or light releasablematerial. The etch-stop layer can be silicon dioxide (SiO2), siliconnitride (Si3N4), silicon oxynitride (SiON), organic film, or metal filmwith wet etching selectivity. The interface layer 102 is deposited usinglamination, PVD, CVD, printing, spin coating, spray coating, sintering,or thermal oxidation. The interface layer 102 is releasable in a laterstep by light or heat. Alternatively, interface layer 102 can be removedby an etching process after removing carrier 100. In one embodiment,interface layer 102 is SiO2/Si3N4 thin film and acts as an etch-stop.

An electrically conductive layer 104 is formed over interface layer 102using a deposition and patterning process to form individual portions orsections 104 a-104 d. FIG. 4 b shows a top or plan view of conductivelayer 104 a-104 d, with conductive layer 104 a being electricallyisolated or partially isolated from conductive layer 104 b-104 d by gap106 which exposes interface layer 102. Conductive layer 104 can be oneor more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitable electricallyconductive material. The deposition of conductive layer 104 uses PVD,CVD, sputtering, electrolytic plating, electroless plating, metalevaporation, metal sputtering, or other suitable metal depositionprocess. In one embodiment, conductive layer 104 a is a solid film forconducting current for later formed conductive pillars. Conductive layer104 b-104 d includes a plated seed layer and under bump metallization(UBM) pads containing multiple layers of selectively plated Ni/Au,titanium (Ti)/Cu, titanium tungsten (TiW)/Cu, Ti/Cu/nickel vanadium(NiV)/Cu, or their combination. UBM pads 104 b-104 d provide bondablepads for bonding with bumps 114, and may further provide a barrier todiffusion and a seed layer for wettability.

In FIG. 4 c, a photoresist layer 108 is deposited over interface layer102 and conductive layer 104. A portion of photoresist layer 108 isexposed and removed by an etching development process. Conductivepillars or posts 110 are formed in the removed portion of photoresist108 over conductive layer 104 a using selective plating or othersuitable process. Conductive pillars 110 are Cu, Al, tungsten (W), Au,solder, or other suitable electrically conductive material. In oneembodiment, conductive pillars 110 are formed by plating Cu in thepatterned areas of photoresist 108. In one embodiment, conductivepillars 110 have a height ranging from 2-120 micrometers (μm).Photoresist 108 is stripped away leaving behind individual conductivepillars 110. In another embodiment, conductive pillars 110 can bereplaced with solder balls or stud bumps.

In FIG. 4 d, semiconductor die 112 from FIGS. 3 a-3 c are mounted to UBMpads 104 b-104 d with bumps 114 in a flipchip arrangement such that theactive surface of semiconductor die 112 is oriented toward carrier 100.Alternatively, bumps or interconnects 114 are formed over UBM pads 104b-104 d rather than over contact pads 98 such that semiconductor die 112is mounted to bumps or interconnects 114 when the semiconductor die ismounted over the UBM pads. In another embodiment, passive components aremounted to UBM pads 104 b-104 d. Accordingly, the same conductive layer104 operates for both flipchip bonding placement and conductive pillarplating.

FIG. 4 e shows an encapsulant or molding compound 116 deposited oversemiconductor die 112, conductive layer 104, interface layer 102, andaround conductive pillars 110 using a paste printing, compressivemolding, transfer molding, liquid encapsulant molding, vacuumlamination, or other suitable applicator. Encapsulant 116 can be polymercomposite material, such as epoxy resin with filler, epoxy acrylate withfiller, or polymer with proper filler. Encapsulant 116 is non-conductiveand environmentally protects the semiconductor device from externalelements and contaminants. Encapsulant 116 has a coefficient of thermalexpansion (CTE) that is adjusted to match that of the base semiconductormaterial, e.g., Si, with a high glass transition temperature (Tg) in therange of 100 to 300 degrees Celsius (° C.) to reduce warpage. The CTE ofencapsulant 116 can be adjusted using a filler such as a powder, fiber,or cloth additive. A suitable encapsulant material is generallycharacterized by good thermal conductivity similar to Si, low-shrinkage,high-resistivity of greater than 1.0 kohm-cm, low-dielectric constant ofless than 3.5, and low-loss tangent of less than 0.02.

Encapsulant 116 undergoes grinding or plasma etching to expose the topsurface of conductive pillars 110 and semiconductor die 112.Alternatively, encapsulant 116 is deposited with a partially exposedmolding technology such that encapsulant 116 does not cover the topsurface of conductive pillars 110 and semiconductor die 112. In eitherinstance, conductive pillars 110 represent a through moldinginterconnect (TMI) structure. A height of the exposed surface ofconductive pillars 110 is less than a height of a backside surface ofsemiconductor die 112. As a result, a height of encapsulant 116 adjacentto the backside surface of semiconductor die 112 is greater than aheight of encapsulant 116 formed over carrier 100 and in a periphery ofconductive pillars 110 outside a footprint of semiconductor die 112. Aportion of a top surface of encapsulant 116 includes a tapered or slopedprofile that extends from a first height of encapsulant 116 formed in aperiphery of conductive pillars 110 to a backside surface ofsemiconductor die 112 at a second height. The second height is greaterthan the first height. In one embodiment, the difference between thefirst height and the second height is in a range of 10-200 μm. Thedifference between the first height and the second height can be changedby removing a portion of the backside surface of semiconductor die 112and a portion of encapsulant 116 in a periphery of the backside of thesemiconductor die with backgrinding or other suitable process.

In FIG. 4 f, an insulation or passivation layer 118 is formed overconductive pillars 110, encapsulant 116, and semiconductor die 112 usingPVD, CVD, screen printing, spin coating, spray coating, sintering orthermal oxidation.

Insulation layer 118 contains one or more layers of SiO2, Si3N4, SiON,tantalum pentoxide (Ta2O5), aluminum oxide (Al2O3), polyimide,benzocyclobutene (BCB), polybenzoxazoles (PBO), or other material havingsimilar insulating and structural properties. In one embodiment,insulation layer 118 is a photosensitive dielectric polymer low-cured atless than 200° C. Insulation layer 118 is conformally applied to,follows the contours of, and uniformly covers conductive pillars 110,encapsulant 116, and semiconductor die 112. In one embodiment, a portionof insulation layer 118 is removed by etching or other suitable processto expose the top surface of conductive pillars 110. The insulationlayer 118 is used to planarize the wafer topography and is optional.

An electrically conductive layer 120 is formed over conductive pillars110 and insulation layer 118 using a patterning and metal depositionprocess such as printing, PVD, CVD, sputtering, electrolytic plating,electroless plating, metal evaporation, metal sputtering, or othersuitable metal deposition process. Conductive layer 120 is one or morelayers of Al, Cu, Sn, Ni, Au, Ag, Ti, or other suitable electricallyconductive material. In one embodiment, conductive layer 120 is amulti-layer RDL structure containing Ti/Cu or Ti/Al alloy. Conductivelayer 120 follows the contour of insulation layer 118, the openings ininsulation layer 118 over conductive pillars 110, and portions ofconductive pillars 110 exposed by the openings in insulation layer 118.Conductive layer 120 operates as an RDL to extend electrical connectionwith respect to conductive pillar 110.

An insulation or passivation layer 122 is formed over insulation layer118 and conductive layer 120 using PVD, CVD, screen printing, spincoating, spray coating, sintering or thermal oxidation. Insulation layer122 contains one or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3,polyimide, BCB, PBO, or other material having similar insulating andstructural properties. In one embodiment, insulation layer 122 is aphotosensitive dielectric polymer low-cured at less than 200° C.Insulation layer 122 is formed over insulation layer 118 and conductivelayer 120 to planarize the wafer topography and protect the conductivelayer. A portion of insulation layer 122 is removed by etching or othersuitable process to expose conductive layer 120 for package levelinterconnection. Additional insulation layers and conductive layers canbe added to the device structure as needed for interconnectfunctionality.

In FIG. 4 g, carrier 100 and interface layer 102 are removed by chemicaletching, mechanical peel-off, CMP, mechanical grinding, thermal bake,laser scanning, or wet stripping. An optional protective layer 124 isformed over conductive layer 120 and insulation layer 122 either beforeor after carrier and interface layer removal. Conductive layer 104 a-104d remains as shown in FIG. 4 b during carrier and interface layerremoval. A portion of conductive layer 104 a is then removed byselective patterning and wet-etching or other suitable process to form adesign pattern including interconnect lines 126 and pads 128 as shown ina cross-sectional view in FIG. 4 h and a plan view in FIG. 4 i.Conductive layer 104 is patterned such that UBM pads 104 b-104 d,interconnect lines 126, and pads 128 together with later formed bumpswill provide electrical connection within the semiconductor device andprovide next level electrical connection to points outside thesemiconductor device. In one embodiment, the removal of portions ofconductive layer 104 a further forms additional circuit components, suchas an inductor.

In FIG. 4 h, an insulation or passivation layer 130 is formed over anactive surface of semiconductor die 112, conductive layer 104, andencapsulant 116 using PVD, CVD, screen printing, spin coating, spraycoating, sintering or thermal oxidation. Insulation layer 130 containsone or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3, polyimide, BCB,PBO, or other material having similar insulating and structuralproperties. In one embodiment, insulation layer 130 is a photosensitivedielectric polymer low-cured at less than 200° C. Insulation layer 130is formed over and protects conductive layer 104. A portion ofinsulation layer 130 is removed by etching or other suitable process toexpose a portion of conductive layer 104.

FIG. 4 i shows a plan view of the semiconductor device includingconductive layer 104, UBM pads 104 b-104 d, interconnect lines 126, pads128, and insulation layer 130 configured such that later formed bumpswill provide electrical connection within the semiconductor device andprovide next level electrical connection to points outside thesemiconductor device.

FIG. 4 j shows further detail of area 132 from FIG. 4 h includingconductive layer 104 a, conductive layer 104 d, and insulation layer130. Conductive layers 104 a-104 d each include stacked top wettinglayer 134, barrier layer 136, and bottom wetting layer 138, such asCu/NiV/Cu, Cu/TiW/Cu, or Cu/Ti/Cu. Adhesion layer 140 is formed betweenthe stacked wetting and barrier layers, and insulation layer 130. In oneembodiment, adhesion layer 140 is a Ti film layer. Alternatively,adhesion layer 140 is TiW, Al, or chromium (Cr). The insulation layer130 is formed over conductive layers 104 a-104 d. A portion of adhesionlayer 140 that is exposed by the openings formed in insulation layer 130is removed by dry etching, wet etching, or other suitable process toexpose bottom wetting layer 138 outside a footprint of insulation layer130.

FIG. 4 k, similar to FIG. 4 j, shows an alternate embodiment of area 132from FIG. 4 h including conductive layer 104 a, conductive layer 104 d,and insulation layer 130. Conductive layers 104 a-104 d include amultiple metal stack with top wetting layer 142, barrier layer 144,optional bottom wetting layer 146, and adhesion layer 148. Adhesionlayer 148 includes a Ti, TiW film, or other suitable material.Conductive layer 150 is formed over adhesion layer 148 using apatterning and metal deposition process such as printing, PVD, CVD,sputtering, electrolytic plating, electroless plating, metalevaporation, metal sputtering, or other suitable metal depositionprocess. Conductive layer 150 can be one or more layers of Al, Cu, Sn,Ni, Au, Ag, or other suitable electrically conductive material. In oneembodiment, conductive layer 150 is plated Cu and is formed by usingconductive layer 104 as seed layer for selective plating. A portion ofconductive layer 150 is removed by etching or other suitable process toform an inductor. A portion of adhesion layer 148 can be removed by dryetching, wet etching, or other suitable process to expose bottom wettinglayer 146 either before or after the formation of conductive layer 150.In either instance, the portion of adhesion layer 148 is removed beforethe formation of insulation layer 130 over conductive layer 150.

FIG. 5 a shows a 3-D FO-WLCSP from FIGS. 4 a-4 k with an electricallyconductive bump material deposited over conductive layer 104 a-104 dusing an evaporation, electrolytic plating, electroless plating, balldrop, or screen printing process. The bump material can be Al, Sn, Ni,Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, with an optionalflux solution. For example, the bump material can be eutectic Sn/Pb,high-lead solder, or lead-free solder. The bump material is bonded toconductive layer 104 a-104 d using a suitable attachment or bondingprocess. In one embodiment, the bump material is reflowed by heating thematerial above its melting point to form spherical balls or bumps 152and 154. In some applications, bumps 152 and 154 are reflowed a secondtime to improve electrical contact to conductive layer 104 a-104 d. Thebumps can also be compression bonded to conductive layer 104 a-104 d.Bumps 152 act as a bridge between interconnect lines 126 and UBM pads104 b-104 d, see e.g., FIGS. 4 i and 5 b. Bumps 154 are made higher thanbumps 152 for next level interconnect without electrically shortingbumps 152. Bumps 152 and 154 represent one type of interconnectstructure that can be formed over conductive layer 104 a-104 d. Theinterconnect structure can also use bond wires, 3-D interconnects,conductive paste, stud bump, micro bump, or other electricalinterconnect. The 3-D FO-WLCSP provides electrical connection forsemiconductor die 112 to external devices through a verticalinterconnect structure including conductive layer 104, TMI conductivepillars 110, conductive layer 120, and bumps 152 and 154.

FIG. 6 shows an alternate embodiment of a 3-D FO-WLCSP similar to the3-D FO-WLCSP from FIGS. 4 a-4 k, with similar elements having the samenumbers. In FIG. 6, conductive layer 156 is formed over conductive layer104 and encapsulant 116 using a patterning and metal deposition processsuch as printing, PVD, CVD, sputtering, electrolytic plating,electroless plating, metal evaporation, metal sputtering, or othersuitable metal deposition process. Conductive layer 156 can be one ormore layers of Al, Cu, Sn, Ni, Au, Ag, or other suitable electricallyconductive material. Conductive layer 156 is formed over conductivelayer 104 and encapsulant 116 after a carrier and interface layersimilar to carrier 100 and interface 102 from FIGS. 4 a-4 f are removed.Conductive layer 156 provides an electrical path between bumps 114 ofsemiconductor die 112, conductive pillars 110, and later formed bumpsfor next level interconnect. Conductive layers 104 and 156 are formed ordeposited together in the same process step. Portions of conductivelayers 104 and 156 are then removed in two separate steps by patterningand etching or other suitable process. A portion of conductive layer 104is removed before the formation of conductive pillars 110. A portion ofconductive layer 156 is removed after the carrier and interface layerare removed such that the remaining portion of conductive layer 156 is aUBM for later formed bumps. The remaining portion is also an RDL thatprovides electrical interconnect between later formed bumps, conductivepillars 110, and semiconductor die 112.

An insulation or passivation layer 158 is formed over conductive layer156 and encapsulant 116 using PVD, CVD, screen printing, spin coating,spray coating, sintering or thermal oxidation. Insulation layer 158contains one or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3,polyimide, BCB, PBO, or other material having similar insulating andstructural properties. In one embodiment, insulation layer 158 is aphotosensitive dielectric polymer low-cured at less than 200° C.Insulation layer 158 is conformally applied to, follows the contours of,and protects, conductive layer 156 and encapsulant 116. A portion ofinsulation layer 158 is removed by etching or other suitable process toexpose a portion of conductive layer 156 for subsequent electricalinterconnect.

An electrically conductive bump material is deposited over conductivelayer 156 using an evaporation, electrolytic plating, electrolessplating, ball drop, or screen printing process. The bump material can beAl, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, withan optional flux solution. For example, the bump material can beeutectic Sn/Pb, high-lead solder, or lead-free solder. The bump materialis bonded to conductive layer 156 using a suitable attachment or bondingprocess. In one embodiment, the bump material is reflowed by heating thematerial above its melting point to form spherical balls or bumps 160.In some applications, bumps 160 are reflowed a second time to improveelectrical contact to conductive layer 156. The bumps can also becompression bonded to conductive layer 156. Bumps 160 represent one typeof interconnect structure that can be formed over conductive layer 156.The interconnect structure can also use bond wires, 3-D interconnects,conductive paste, stud bump, micro bump, or other electricalinterconnect. Bumps 160 of the 3-D FO-WLCSP provide electricalconnection for semiconductor die 112 to external devices through avertical interconnect structure including conductive layers 104 and 156,TMI conductive pillars 110, and conductive layer 120.

FIG. 7 shows further detail of area 162 from FIG. 6 including conductivelayers 104 and 156. Conductive layers 104 a-104 d each include amultiple metal stack with top wetting layer 163 and barrier layer 164.In one embodiment, wetting layer 163 is Cu and barrier layer 164 is NiVor Ni. Similarly, conductive layer 156 also includes a multiple metalstack with an optional middle adhesion layer 165, optional barrier layer166, bottom wetting layer 167, and bottom adhesive layer 168. In oneembodiment, adhesion layer 165 is Ti or TiW, barrier layer 166 is NiV orNi, wetting layer 167 is Cu, and adhesive layer 168 is Ti. Conductivelayers 104 and 156 are formed as separate layers, or alternatively, theconductive layers are formed or deposited together in the same processstep. When conductive layers 104 and 156 are formed as separate layers,conductive layer 104 is formed and patterned before the formation ofconductive pillars 110, and conductive layer 156 is formed after theremoval of a temporary carrier and interface layer similar to carrier100 and interface layer 102 shown in FIGS. 4 a-4 f. When conductivelayers 104 and 156 are formed in the same process step, portions of theconductive layers are removed in two separate steps by patterning andetching or other suitable process. A portion of conductive layer 104 isremoved from wetting layer 163 and barrier layer 164 before theformation of conductive pillars 110. A portion of conductive layer 156is removed from adhesive layer 168 such that the remaining portion ofconductive layer 156 is a UBM for later formed bumps. The remainingportion of conductive layer 156 is also an RDL that provides electricalinterconnect between later formed bumps, conductive pillars 110, andsemiconductor die 112. Conductive layer 156 is configured as a UBM andRDL after the carrier and interface layer are removed.

FIG. 8 shows an alternate embodiment of an interconnect structure for a3-D FO-WLCSP similar to the 3-D FO-WLCSP from FIGS. 4 a-4 k. Anelectrically conductive layer 170, similar to conductive layer 104 shownin FIGS. 4 a-4 k, is formed over a carrier and interface layer to formindividual portions or sections 170 a-170 d. Conductive layer 170 a iselectrically isolated from conductive layers 170 b-170 d. In oneembodiment, conductive layers 170 b-170 d include a plated seed layerand UBM pads containing multiple layers of selectively plated Ni/Au,Ti/Cu, or Ti/Cu/NiV/Cu.

Conductive pillars or posts 176, similar to conductive posts 110 in FIG.4 c, are formed over conductive layer 170 a. Semiconductor die 172,similar to semiconductor die 112 in FIG. 4 d, are mounted to UBM pads170 b-170 d with bumps 174 in a flipchip arrangement. In anotherembodiment, passive components can be mounted to UBM pads 170 b-170 d.

A first encapsulant or molding compound 178, similar to encapsulant 116in FIG. 4 e, is deposited over semiconductor die 172, over conductivelayer 170, over a temporary carrier and interface layer similar tocarrier 100 and interface layer 102, and around conductive pillars 176.Encapsulant 178 is deposited using a paste printing, compressivemolding, transfer molding, liquid encapsulant molding, vacuumlamination, or other suitable applicator. Encapsulant 178 can be polymercomposite material, such as epoxy resin with filler, epoxy acrylate withfiller, or polymer with proper filler. Encapsulant 178 is non-conductiveand environmentally protects the semiconductor device from externalelements and contaminants. Encapsulant 178 has a CTE that is adjusted tomatch that of the base semiconductor material, e.g., Si, with a high Tgin the range of 100° C. to 300° C. to reduce warpage. The CTE ofencapsulant 178 can be adjusted using a filler such as a powder, fiber,or cloth additive. A suitable encapsulant material is generallycharacterized by good thermal conductivity similar to Si, low-shrinkage,high-resistivity of greater than 1.0 kohm-cm, low-dielectric constant ofless than 3.5, and low-loss tangent of less than 0.02.

Encapsulant 178 undergoes grinding or plasma etching to expose the topsurface of conductive pillars 176 and semiconductor die 172.Alternatively, encapsulant 178 is deposited with a partially exposedmolding technology such that encapsulant 178 does not cover the topsurface of conductive pillars 176 and semiconductor die 172. In eitherinstance, conductive pillars 176 represent a TMI structure. A height ofthe exposed surface of conductive pillars 176 is less than a height of abackside surface of semiconductor die 172. As a result, a height ofencapsulant 178 adjacent to the backside surface of semiconductor die172 is greater than a height of encapsulant 178 formed over the carrierand in a periphery of conductive pillars 176 outside a footprint ofsemiconductor die 172. A portion of a top surface 179 of encapsulant 178includes a tapered or sloped profile that extends from a first height ofencapsulant 178 formed in a periphery of conductive pillars 176 to abackside surface of semiconductor die 172 at a second height. The secondheight is greater than the first height. In one embodiment, thedifference between the first height and the second height is in a rangeof 10-200 μm. The difference between the first height and the secondheight can be changed by removing a portion of the backside surface ofsemiconductor die 172 and a portion of encapsulant 178 in a periphery ofthe backside of semiconductor die with backgrinding or other suitableprocess.

An electrically conductive bump material is deposited over conductivepillars 176 using an evaporation, electrolytic plating, electrolessplating, ball drop, or screen printing process. The bump material can beAl, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, withan optional flux solution. For example, the bump material can beeutectic Sn/Pb, high-lead solder, or lead-free solder. The bump materialis bonded to conductive pillars 176 using a suitable attachment orbonding process. In one embodiment, the bump material is reflowed byheating the material above its melting point to form spherical balls orbumps 180. In some applications, bumps 180 are reflowed a second time toimprove electrical contact to conductive pillars 176. The bumps can alsobe compression bonded to conductive pillars 176. Bumps 180 represent onetype of interconnect structure that can be formed over conductivepillars 176. The interconnect structure can also use conductive paste,stud bump, micro bump, or other electrical interconnect. Accordingly,bumps 180 are formed over, and are electrically connected to, conductivepillars 176 to form a TMI structure with increased height or standoff.

A second encapsulant or molding compound 181 is deposited over firstencapsulant 178, over semiconductor die 172, and around bumps 180 usinga paste printing, compressive molding, transfer molding, liquidencapsulant molding, vacuum lamination, or other suitable applicator.Encapsulant 181 can be polymer composite material, such as epoxy resinwith filler, epoxy acrylate with filler, or polymer with proper filler.Encapsulant 181 is non-conductive and environmentally protects thesemiconductor device from external elements and contaminants.Encapsulant 181 has a CTE that is adjusted to match that of the basesemiconductor material, e.g., Si, with a high Tg in the range of 100° C.to 300° C. to reduce warpage. The CTE of encapsulant 181 can be adjustedusing a filler such as a powder, fiber, or cloth additive. A suitableencapsulant material is generally characterized by good thermalconductivity similar to Si, low-shrinkage, high-resistivity of greaterthan 1.0 kohm-cm, low-dielectric constant of less than 3.5, and low-losstangent of less than 0.02.

Encapsulant 181 includes a first or bottom surface 182 that isconformally applied to, and follows the contours of, the top surface 179of encapsulant 178 including the tapered or sloped profile that extendsfrom a first height in a periphery of conductive pillars 176 to abackside surface of semiconductor die 172 at a second height.Encapsulant 181 also includes a second or top surface 183 formedopposite the first or bottom surface 182. Second or top surface 183 isplanar and does not parallel the contour of the first or bottom surface182. In one embodiment, encapsulant 181 is deposited with a partiallyexposed molding technology such that the second or top surface 183 ofencapsulant 181 does not cover a top surface or portion of bumps 180.Alternatively, the second or top surface 183 of encapsulant 181 doescover a top surface or portion of bumps 180, and encapsulant 181undergoes grinding or plasma etching to remove a portion of encapsulant181 to expose the top surface or portion of bumps 180. In eitherinstance, bumps 180 are exposed as part of a TMI structure havingincreased height or standoff with respect to a TMI structure includingonly conductive pillars 176.

An electrically conductive layer 184 is formed over bumps 180 andencapsulant 181 using a patterning and metal deposition process such asprinting, PVD, CVD, sputtering, electrolytic plating, electrolessplating, metal evaporation, metal sputtering, or other suitable metaldeposition process. Conductive layer 184 is one or more layers of Al,Cu, Sn, Ni, Au, Ag, Ti, or other suitable electrically conductivematerial. In one embodiment, conductive layer 184 is a multi-layer RDLstructure containing Ti/Cu or Ti/Al alloy. Conductive layer 184 isconformally applied to, and follows the contour of, a top surface orportion of bumps 180 and second or top surface 183 of encapsulant 181.Conductive layer 184 operates as an RDL to extend electrical connectionwith respect to bump 180 and conductive pillar 176.

An insulation or passivation layer 186 is formed over second encapsulant181 and conductive layer 184 using PVD, CVD, screen printing, spincoating, spray coating, sintering or thermal oxidation. Insulation layer186 contains one or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3,polyimide, BCB, PBO, or other material having similar insulating andstructural properties. In one embodiment, insulation layer 186 is aphotosensitive dielectric polymer low-cured at less than 200° C.Insulation layer 186 is formed over encapsulant 181 and conductive layer184 to planarize the wafer topography and protect the conductive layer.A portion of insulation layer 186 is removed by etching or othersuitable process to expose conductive layer 184 for package levelinterconnection. Additional insulation layers and conductive layers canbe added to the device structure as needed for interconnectfunctionality.

The carrier and interface layer, similar to carrier 100 and interfacelayer 102 in FIG. 4 g, are removed by chemical etching, mechanicalpeel-off, CMP, mechanical grinding, thermal bake, laser scanning, or wetstripping. A portion of conductive layer 170 a is then removed byselective patterning and wet-etching or other suitable process to form adesign pattern including interconnect lines and pads similar tointerconnect lines 126 and pads 128 shown in FIG. 4 h and FIG. 4 i.Conductive layer 170 a can also be patterned to form additional circuitcomponents, such as an inductor.

An insulation or passivation layer 188, similar to insulation layer 130in FIG. 4 h, is formed over an active surface of semiconductor die 172,conductive layer 170, and encapsulant 178. Insulation layer 188 isformed over and protects conductive layer 170. A portion of insulationlayer 188 is removed by etching or other suitable process to expose aportion of conductive layer 170.

An electrically conductive bump material is deposited over conductivelayer 170 a-170 d to form spherical balls or bumps 190 and 192, similarto the process of forming bumps 152 and 154 shown in FIG. 5 a. Bumps 190act as a bridge between interconnect lines and UBM pads, similar tointerconnect lines 126 and UBM pads 128 in FIGS. 4 i and 5 b. Bumps 192are made larger than bumps 190 for next level interconnect withoutelectrically shorting bumps 190. Bumps 190 and 192 represent one type ofinterconnect structure that can be formed over conductive layer 170a-170 d. The interconnect structure can also use bond wires, 3-Dinterconnects, conductive paste, stud bump, micro bump, or otherelectrical interconnect. The 3-D FO-WLCSP provides electrical connectionfor semiconductor die 172 to external devices through a verticalinterconnect structure including conductive layer 170, TMI conductivepillars 176, conductive layer 184, and bumps 180, 190, and 192.

FIGS. 9 a-9 c show an alternate embodiment of an interconnect structurefor a 3-D FO-WLCSP similar to the 3-D FO-WLCSP from FIG. 6. FIG. 9 adiffers from FIG. 6 with the inclusion of conductive layer 218, which isdiscussed in more detail below. In FIG. 9 a, an electrically conductivelayer 200, similar to conductive layer 104 shown in FIG. 6, is formedover a carrier and interface layer to form individual portions orsections 200 a-200 d. Individual portions or sections 200 a-200 d areshown in plan view in FIG. 9 b. Conductive layer 200 a is electricallyisolated from conductive layers 200 b-200 d by gap 203. In oneembodiment, conductive layers 200 b-200 d include a plated seed layerand UBM pads containing multiple layers of selectively plated Ni/Au,Ti/Cu, or Ti/Cu/NiV/Cu.

Conductive pillars or posts 206, similar to conductive posts 110 in FIG.6, are formed over conductive layer 200 a. Semiconductor die 202,similar to semiconductor die 112 in FIG. 6, are mounted to UBM pads 200b-200 d with bumps 204 in a flipchip arrangement. In another embodiment,passive components can be mounted to UBM pads 200 b-200 d. Encapsulant208, insulation layer 210, conductive layer 212, and insulation layer214 shown in FIG. 9 a are analogous to encapsulant 116, insulation layer118, conductive layer 120, and insulation layer 122, respectively, asshown in FIGS. 4 a-4 k and FIG. 6.

After forming or depositing material over the carrier and interfacelayer, e.g., providing encapsulant 208, insulation layer 210, conductivelayer 212, and insulation layer 214, the carrier and interface layer,similar to carrier 100 and interface layer 102 in FIG. 4 g, are removedby chemical etching, mechanical peel-off, CMP, mechanical grinding,thermal bake, laser scanning, or wet stripping. Conductive layers 200a-200 d remain as shown in FIG. 9 b during carrier and interface layerremoval. A portion of conductive layer 200 a is then removed byselective patterning and wet-etching or other suitable process to form adesign pattern including interconnect lines and pads shown in thecross-sectional view of FIG. 9 a and the plan view of FIG. 9 c.Conductive layer 200 a can also be patterned to form additional circuitcomponents, such as an inductor.

A conductive layer 218 is formed over conductive layer 200 andencapsulant 208 using a patterning and metal deposition process such asprinting, PVD, CVD, sputtering, electrolytic plating, electrolessplating, metal evaporation, metal sputtering, or other suitable metaldeposition process. Conductive layer 218 can be one or more layers ofAl, Cu, Sn, Ni, Au, Ag, or other suitable electrically conductivematerial. Conductive layer 218 is formed over conductive layer 200 andencapsulant 208 after a portion of conductive layer 200 a is removed toform the interconnect lines 216 and pads shown in FIG. 9 c. Conductivelayer 218 provides an electrical path between bumps 204 of semiconductordie 202, conductive pillars 206, and later formed bumps for next levelinterconnect. Thus, conductive layer 218 provides interconnection amongsemiconductor die 202 and points external to the semiconductor dierather than using bumps, such as bumps 152 shown in FIG. 5 a to provideelectrical interconnect. Accordingly, conductive layers 200 and 218shown in FIG. 9 a are formed in different process steps. Conductivelayer 200 is formed over the carrier and interface layer. Conductivelayer 218 is formed over conductive layer 200 after the removal of thecarrier and interface layer. Thus, the forming of conductive layer 218in FIG. 9 differs from the formation of conductive layer 156 from FIG. 6because conductive layer 156 is formed over the carrier and interfacelayer with, and in the same process step as, conductive layer 104.

FIG. 9 a further shows an insulation or passivation layer 220 formedover conductive layer 218 and encapsulant 208 using PVD, CVD, screenprinting, spin coating, spray coating, sintering or thermal oxidation.Insulation layer 220 contains one or more layers of SiO2, Si3N4, SiON,Ta2O5, Al2O3, polyimide, BCB, PBO, or other material having similarinsulating and structural properties. In one embodiment, insulationlayer 220 is a photosensitive dielectric polymer low-cured at less than200° C. Insulation layer 220 is conformally applied to, follows thecontours of, and protects, conductive layer 218 and encapsulant 208. Aportion of insulation layer 220 is removed by etching or other suitableprocess to expose a portion of conductive layer 218 for subsequentelectrical interconnect.

An electrically conductive bump material is deposited over conductivelayer 218 using an evaporation, electrolytic plating, electrolessplating, ball drop, or screen printing process. The bump material can beAl, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, withan optional flux solution. For example, the bump material can beeutectic Sn/Pb, high-lead solder, or lead-free solder. The bump materialis bonded to conductive layer 218 using a suitable attachment or bondingprocess. In one embodiment, the bump material is reflowed by heating thematerial above its melting point to form spherical balls or bumps 222.In some applications, bumps 222 are reflowed a second time to improveelectrical contact to conductive layer 218. The bumps can also becompression bonded to conductive layer 218. Bumps 222 represent one typeof interconnect structure that can be formed over conductive layer 218.The interconnect structure can also use bond wires, 3-D interconnects,conductive paste, stud bump, micro bump, or other electricalinterconnect. Bumps 222 of the 3-D FO-WLCSP provide electricalconnection for semiconductor die 202 to external devices through avertical interconnect structure including conductive layers 200 and 218,TMI conductive pillars 206, and conductive layer 212.

FIGS. 10 a-10 b illustrate another process of forming an interconnectstructure for 3-D FO-WLCSP. In FIG. 10 a, a substrate or wafer 230contains dummy or sacrificial base material such as Si, polymer, polymercomposite, metal, ceramic, glass, glass epoxy, beryllium oxide, or othersuitable low-cost, rigid material or bulk semiconductor material forstructural support.

An interface layer 232 is deposited over carrier 230. The interfacelayer 232 can be temporary bonding film or etch-stop layer. Thetemporary bonding film can be either heat or light releasable material.The etch-stop layer can be SiO2, Si3N4, SiON, organic film, or metalfilm. The interface layer 232 is deposited using lamination, PVD, CVD,printing, spin coating, spray coating, sintering or thermal oxidation.In one embodiment, interface layer 232 is SiO2/Si3N4 thin film and actsas an etch-stop.

A photoresist layer is deposited over interface layer 232. A portion ofthe photoresist is exposed and removed by an etching process. Conductivepillars or posts 234 are formed in the removed portion of thephotoresist using a photolithographic process. Conductive pillars orposts 234 are formed in the removed portion of the photoresist overinterface layer 232 using selective plating or other suitable process.Conductive pillars 234 can be Cu, Al, W, Au, solder, or other suitableelectrically conductive material. In one embodiment, conductive pillars234 are formed by plating Cu in the patterned areas of the photoresist.Conductive pillars 234 have a height ranging from 2-120 μm. Thephotoresist is stripped away leaving behind individual conductivepillars 234. In another embodiment, TMI conductive pillars 234 can bereplaced with solder balls or stud bumps.

A plurality of semiconductor die 236 with contact pads 237 are mountedto interface layer 232 with pre-applied and strippable adhesive 238.Semiconductor die 236 each include a substrate with an active regioncontaining analog or digital circuits implemented as active devices,passive devices, conductive layers, and dielectric layers formed withinthe semiconductor die and electrically interconnected according to theelectrical design of the semiconductor die. For example, the circuit mayinclude one or more transistors, diodes, inductors, capacitors,resistors, and other circuit elements formed within the active region ofsemiconductor die 236 to implement analog circuits or digital circuits,such as DSP, ASIC, memory, or other signal processing circuit.

Contact pads 237 are formed over an active surface of semiconductor die236 using PVD, CVD, electrolytic plating, electroless plating process,or other suitable metal deposition process. Contact pads 237 can be oneor more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitable electricallyconductive material. Contact pads 237 electrically connected to thecircuits on the active surface. Contact pads 237 can be disposedside-by-side a first distance from the edge of semiconductor die 236.Alternatively, contact pads 237 can be offset in multiple rows such thata first row of contact pads is disposed a first distance from the edgeof the die, and a second row of contact pads alternating with the firstrow is disposed a second distance from the edge of the die.

An encapsulant or molding compound 240, similar to encapsulant 116 inFIG. 4 e, is deposited over semiconductor die 236, over carrier 230 andinterface layer 232, and around conductive pillars 234. Encapsulant 240is deposited using a paste printing, compressive molding, transfermolding, liquid encapsulant molding, vacuum lamination, or othersuitable applicator. Encapsulant 240 can be polymer composite material,such as epoxy resin with filler, epoxy acrylate with filler, or polymerwith proper filler. Encapsulant 240 is non-conductive andenvironmentally protects the semiconductor device from external elementsand contaminants. Encapsulant 240 has a CTE that is adjusted to matchthat of the base semiconductor material, e.g., Si, with a high Tg in therange of 100° C. to 300° C. to reduce warpage. The CTE of encapsulant240 can be adjusted using a filler such as a powder, fiber, or clothadditive. A suitable encapsulant material is generally characterized bygood thermal conductivity similar to Si, low-shrinkage, high-resistivityof greater than 1.0 kohm-cm, low-dielectric constant of less than 3.5,and low-loss tangent of less than 0.02.

Encapsulant 240 undergoes grinding or plasma etching to expose a topsurface of conductive pillars 234 and a backside surface ofsemiconductor die 236. Alternatively, encapsulant 240 is deposited witha partially exposed molding technology such that encapsulant 240 doesnot cover the top surface of conductive pillars 234 and semiconductordie 236. In either instance, conductive pillars 234 represent a TMIstructure. A height of the exposed surface of conductive pillars 234 isless than a height of a backside surface of semiconductor die 236. As aresult, a height of encapsulant 240 adjacent to the backside surface ofsemiconductor die 236 is greater than a height of encapsulant 240 formedover carrier 230 and in a periphery of conductive pillars 234 outside afootprint of semiconductor die 236. A portion of a top surface ofencapsulant 240 includes a tapered or sloped profile that extends from afirst height of encapsulant 240 formed in a periphery of conductivepillars 234 to a backside surface of semiconductor die 236 at a secondheight. The second height is greater than the first height. In oneembodiment, the difference between the first height and the secondheight is in a range of 10-200 μm. The difference between the firstheight and the second height can be changed by removing a portion of thebackside surface of semiconductor die 236 and a portion of encapsulant240 in a periphery of the backside of semiconductor die 236 withbackgrinding or other suitable process.

An insulation or passivation layer 242 is formed over conductive pillars234, encapsulant 240, and semiconductor die 236 using PVD, CVD, screenprinting, spin coating, spray coating, sintering or thermal oxidation.Insulation layer 242 contains one or more layers of SiO2, Si3N4, SiON,Ta2O5, Al2O3, polyimide, BCB, PBO, or other material having similarinsulating and structural properties. In one embodiment, insulationlayer 242 is a photosensitive dielectric polymer low-cured at less than200° C. Insulation layer 242 is conformally applied to, follows thecontours of, and uniformly covers conductive pillars 234, encapsulant240, and semiconductor die 236. In one embodiment, a portion ofinsulation layer 242 is removed by etching or other suitable process toexpose a top surface of conductive pillars 234. The insulation layer 242is used to planarize the wafer topography and is optional.

An electrically conductive layer 244 is formed over conductive pillars234 and insulation layer 242 using a patterning and metal depositionprocess such as printing, PVD, CVD, sputtering, electrolytic plating,electroless plating, metal evaporation, metal sputtering, or othersuitable metal deposition process. Conductive layer 244 is one or morelayers of Al, Cu, Sn, Ni, Au, Ag, Ti, or other suitable electricallyconductive material. In one embodiment, conductive layer 244 is amulti-layer RDL structure containing Ti/Cu or Ti/Al alloy. Conductivelayer 244 follows the contour of insulation layer 242, the openings ininsulation layer 242 over conductive pillars 234, and portions ofconductive pillars 234 exposed by the openings in insulation layer 242.Conductive layer 244 operates as an RDL to extend electrical connectionwith respect to conductive pillar 234.

An insulation or passivation layer 246 is formed over insulation layer242 and conductive layer 244 using PVD, CVD, screen printing, spincoating, spray coating, sintering or thermal oxidation. Insulation layer246 contains one or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3,polyimide, BCB, PBO, or other material having similar insulating andstructural properties. In one embodiment, insulation layer 246 is aphotosensitive dielectric polymer low-cured at less than 200° C.Insulation layer 246 is formed over insulation layer 242 and conductivelayer 244 to planarize the wafer topography and protect the conductivelayer. A portion of insulation layer 246 is removed by etching or othersuitable process to expose conductive layer 244 for package levelinterconnection. Additional insulation layers and conductive layers canbe added to the device structure as needed for interconnectfunctionality.

In FIG. 10 b, carrier 230, interface layer 232, and adhesive 238 areremoved by chemical etching, mechanical peel-off, CMP, mechanicalgrinding, thermal bake, laser scanning, or wet stripping. An optionalprotective layer can be formed over conductive layer 244 and insulationlayer 246 opposite carrier 230 either before or after the removal of thecarrier and interface layer 232.

An insulation or passivation layer 248 is formed over an active surfaceof semiconductor die 236, conductive pillars 234, and encapsulant 240using PVD, CVD, screen printing, spin coating, spray coating, sinteringor thermal oxidation. Insulation layer 248 contains one or more layersof SiO2, Si3N4, SiON, Ta2O5, Al2O3, polyimide, BCB, PBO, or othermaterial having similar insulating and structural properties. In oneembodiment, insulation layer 248 is a photosensitive dielectric polymerlow-cured at less than 200° C. Insulation layer 248 is formed over andprotects conductive pillars 234 and semiconductor die 236. A portion ofinsulation layer 248 is removed by etching or other suitable process toexpose a bottom portion of conductive pillar 234 and contact pads 237.

An electrically conductive layer 250 is formed over conductive pillars234, contact pads 237, and insulation layer 248 using a patterning andmetal deposition process such as printing, PVD, CVD, sputtering,electrolytic plating, electroless plating, metal evaporation, metalsputtering, or other suitable metal deposition process. Conductive layer250 is one or more layers of Al, Cu, Sn, Ni, Au, Ag, Ti, or othersuitable electrically conductive material. In one embodiment, conductivelayer 250 is a multi-layer RDL structure containing Ti/Cu or Ti/Alalloy. Conductive layer 250 follows the contour of insulation layer 248,the openings in insulation layer 248 over conductive pillars 234, andportions of conductive pillars 234 exposed by the openings in insulationlayer 248. Conductive layer 250 operates as an RDL to extend electricalconnection with respect to conductive pillar 234 and semiconductor die236.

An insulation or passivation layer 252 is formed over conductive layer250 and insulation layer 248 using PVD, CVD, screen printing, spincoating, spray coating, sintering or thermal oxidation. Insulation layer252 contains one or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3,polyimide, BCB, PBO, or other material having similar insulating andstructural properties. In one embodiment, insulation layer 252 is aphotosensitive dielectric polymer low-cured at less than 200° C.Insulation layer 252 is formed over and protects conductive layer 250. Aportion of insulation layer 252 is removed by etching or other suitableprocess to expose a portion of conductive layer 250.

An electrically conductive bump material is deposited over conductivelayer 250 using an evaporation, electrolytic plating, electrolessplating, ball drop, or screen printing process. The bump material can beAl, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, withan optional flux solution. For example, the bump material can beeutectic Sn/Pb, high-lead solder, or lead-free solder. The bump materialis bonded to conductive layer 250 using a suitable attachment or bondingprocess. In one embodiment, the bump material is reflowed by heating thematerial above its melting point to form spherical balls or bumps 254.In some applications, bumps 254 are reflowed a second time to improveelectrical contact to conductive layer 250. The bumps can also becompression bonded to conductive layer 250. Bumps 254 represent one typeof interconnect structure that can be formed over conductive layer 250.The interconnect structure can also use bond wires, 3-D interconnects,conductive paste, stud bump, micro bump, or other electricalinterconnect. Bumps 254 of the 3-D FO-WLCSP provide electricalconnection for semiconductor die 236 to external devices through avertical interconnect structure including conductive layer 244,conductive layer 250, and TMI conductive pillars 234.

FIG. 11 shows an alternate embodiment of a 3-D FO-WLCSP similar to the3-D FO-WLCSP from FIGS. 4 a-4 k, with similar elements having the samenumbers. FIG. 11 differs from FIGS. 4 a-4 k in that encapsulant 260remains disposed over semiconductor die 112 rather than exposing abackside surface of the semiconductor die with respect to theencapsulant as shown, e.g., in FIG. 4 e.

In FIG. 11 an encapsulant or molding compound 260, similar toencapsulant 116 in FIG. 4 e, is deposited over semiconductor die 112,over a carrier and interface layer, and around conductive pillars 110.Encapsulant 260 is deposited using a paste printing, compressivemolding, transfer molding, liquid encapsulant molding, vacuumlamination, or other suitable applicator. Encapsulant 260 can be polymercomposite material, such as epoxy resin with filler, epoxy acrylate withfiller, or polymer with proper filler. Encapsulant 260 is non-conductiveand environmentally protects the semiconductor device from externalelements and contaminants. Encapsulant 260 has a CTE that is adjusted tomatch that of the base semiconductor material, e.g., Si, with a high Tgin the range of 100° C. to 300° C. to reduce warpage. The CTE ofencapsulant 260 can be adjusted using a filler such as a powder, fiber,or cloth additive. A suitable encapsulant material is generallycharacterized by good thermal conductivity similar to Si, low-shrinkage,high-resistivity of greater than 1.0 kohm-cm, low-dielectric constant ofless than 3.5, and low-loss tangent of less than 0.02.

Encapsulant 260 undergoes grinding or plasma etching to expose the topsurface of conductive pillars 110. The grinding and etching does notexpose a backside surface of semiconductor die 112 such that a layer ofencapsulant 260 remains over an entire backside surface of, andpassivates, semiconductor die 112. Alternatively, encapsulant 260 isdeposited with a partially exposed molding technology such thatencapsulant 260 does not cover the top surface of conductive pillars110, but does cover a backside surface of semiconductor die 112. Ineither instance, conductive pillars 110 represent a TMI structure with aportion of conductive pillar 110 being exposed from encapsulant 260. Aheight of the exposed surface of conductive pillars 110 is less than aheight of a backside surface of semiconductor die 112. As a result, aheight of encapsulant 260 over the backside surface of semiconductor die112 is greater than a height of encapsulant 260 formed in a periphery ofconductive pillars 110 outside a footprint of semiconductor die 112. Aportion of a top surface of encapsulant 260 includes a tapered or slopedprofile that extends from a first height of encapsulant 260 formed in aperiphery of conductive pillars 110 to over a backside surface ofsemiconductor die 112 at a second height. The second height is greaterthan the first height. In one embodiment, the difference between thefirst height and the second height is in a range of 10-200 μm. Thedifference between the first height and the second height can be changedby removing a portion of encapsulant 260 over the backside surface ofsemiconductor die 112.

FIG. 12 shows an alternate embodiment of a 3-D FO-WLCSP similar to the3-D FO-WLCSP from FIGS. 10 a-10 b, with similar elements having the samenumbers. FIG. 12 differs from FIGS. 10 a-10 b in that encapsulant 262remains disposed over semiconductor die 236 rather than exposing abackside surface of the semiconductor die with respect to encapsulant240 shown in FIGS. 10 a-10 b.

In FIG. 12, an encapsulant or molding compound 262, similar toencapsulant 240 shown in FIGS. 10 a-10 b, is deposited oversemiconductor die 236, over a carrier and interface layer, and aroundconductive pillars 234. Encapsulant 262 is deposited using a pasteprinting, compressive molding, transfer molding, liquid encapsulantmolding, vacuum lamination, or other suitable applicator. Encapsulant262 can be polymer composite material, such as epoxy resin with filler,epoxy acrylate with filler, or polymer with proper filler. Encapsulant262 is non-conductive and environmentally protects the semiconductordevice from external elements and contaminants. Encapsulant 262 has aCTE that is adjusted to match that of the base semiconductor material,e.g., Si, with a high Tg in the range of 100° C. to 300° C. to reducewarpage. The CTE of encapsulant 262 can be adjusted using a filler suchas a powder, fiber, or cloth additive. A suitable encapsulant materialis generally characterized by good thermal conductivity similar to Si,low-shrinkage, high-resistivity of greater than 1.0 kohm-cm,low-dielectric constant of less than 3.5, and low-loss tangent of lessthan 0.02.

Encapsulant 262 undergoes grinding or plasma etching to expose the topsurface of conductive pillars 234. The grinding and etching does notexpose a surface of semiconductor die 236 such that a layer ofencapsulant 262 remains over an entire backside surface of, andpassivates, semiconductor die 236. Alternatively, encapsulant 262 isdeposited with a partially exposed molding technology such thatencapsulant 262 does not cover the top surface of conductive pillars234, but does cover a backside surface of semiconductor die 236. Ineither instance, conductive pillars 234 represent a TMI structure with aportion of conductive pillar 234 being exposed from encapsulant 262. Aheight of the exposed surface of conductive pillars 234 is less than aheight of a backside surface of semiconductor die 236. As a result, aheight of encapsulant 262 over the backside surface of semiconductor die236 is greater than a height of encapsulant 262 formed in a periphery ofconductive pillars 234 outside a footprint of semiconductor die 236. Aportion of a top surface of encapsulant 262 includes a tapered or slopedprofile that extends from a first height of encapsulant 262 formed in aperiphery of conductive pillars 234 to over a backside surface ofsemiconductor die 236 at a second height. The second height is greaterthan the first height. In one embodiment, the difference between thefirst height and the second height is in a range of 10-200 μm. Thedifference between the first height and the second height can be changedby removing a portion of encapsulant 262 over the backside surface ofsemiconductor die 236 and a portion of encapsulant 262 in a periphery ofthe backside of semiconductor.

FIGS. 13 a-13 x illustrate, in relation to FIGS. 1 and 2 a-2 c, anotherprocess of forming a vertical interconnect structure for a 3-D FO-WLCSP.In FIG. 13 a, a substrate or temporary carrier 270 contains dummy orsacrificial base material such as Si, polymer, polymer composite, metal,ceramic, glass, glass epoxy, beryllium oxide, or other suitablelow-cost, rigid material or bulk semiconductor material for structuralsupport.

An interface layer or double-sided carrier tape 272 is formed overcarrier 270 as a temporary adhesive bonding film or etch-stop layer. Ascarrier tape, interface layer 272 can be either heat or light releasablematerial. In an alternate embodiment, interface layer 272 is an etchstop layer of SiO2, Si3N4, SiON, organic film, or metal film with wetetching selectivity. Interface layer 272 is deposited using lamination,PVD, CVD, printing, spin coating, spray coating, sintering thermaloxidation, or other suitable process.

In FIG. 13 b, a semiconductor die 276, similar to semiconductor die 112from FIGS. 3 a-3 c is mounted over carrier 270 with an active surface ofthe semiconductor die oriented toward substrate 270 and interface layer272. Semiconductor die 276 includes contact pads 277 formed over theactive surface of semiconductor die 276. Contact pads 277 are made witha conductive material such as Al, Cu, Sn, Ni, Au, or Ag, and areelectrically connected to circuit elements formed within semiconductordie 276. Contact pads 277 are formed by PVD, CVD, electrolytic plating,electroless plating, or other suitable process. An insulation orpassivation layer 278 is formed over the active surface of semiconductordie 276. Insulation layer 278 is conformally applied over semiconductordie 276 using PVD, CVD, screen printing, spin coating, spray coating,sintering or thermal oxidation. Insulation layer 278 contains one ormore layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3, or other material havingsimilar insulating and structural properties. Insulation layer 278covers and protects one or more transistors, diodes, or other circuitelements formed within the active surface of semiconductor die 276including IPDs, such as inductors, capacitors, and resistors. A portionof insulation layer 278 is removed from over a portion of contact pads277. The openings in insulating layer 278 over contact pads 277facilitate future electrical interconnect with semiconductor die 276.

Leading with the active surface of semiconductor die 276, thesemiconductor die is mounted over carrier 270 and interface layer 272.Insulation layer 278 contacts interface layer 272 including a portion ofinsulation layer 278 in a periphery of, and around, the openings ininsulation layer 278 to prevent subsequently formed encapsulant fromcontacting contact pads 277.

In FIG. 13 c, printed dots or nodules 280 are formed on interface layer272 and in a periphery of semiconductor die 276 with screen printing,jetting, or other suitable process. Printed dots 280 are a solventremovable material such as a photoresist layer, dry film, or paste thatis removed by an etching process after exposure to a 150° C. heattreatment for one hour. Alternatively, printed dots 280 are a waterremovable material after exposure to a 150° C. heat treatment for onehour. Printed dots 280 are formed before semiconductor 276 is mountedover carrier 270 and interface layer 272. Alternatively, printed dots280 are formed after semiconductor 276 is mounted over carrier 270 andinterface layer 272. Printed dots 280 include a round or circular shape,a ring shape, a dam configuration, a straight line shape, or any othersuitable shape according to the configuration and design of theapplication. Printed dots 280 provide a cavity or void in a later formedencapsulant as discussed in further detail below.

FIGS. 13 d-13 e, similar to FIGS. 13 b-13 c, show an alternateembodiment including a temporary planarization and protection layer 282formed over insulation layer 278. While FIGS. 13 d-13 w show a processflow for a semiconductor device including the use of temporaryplanarization layer 282, the temporary planarization layer is optional,and steps similar to those shown in FIGS. 13 d-13 w are used to form a3-D FO-WLCSP device without the use of temporary planarization layer282. Accordingly, any of the embodiments presented in the figures can bemade with or without temporary planarization layer 282. Temporaryplanarization layer 282 is conformally applied over, and follows thecontours of, insulation layer 278 with spin coating, lamination, screenprinting, slit coating, spray coating, or other suitable process.Temporary planarization layer 282 is a solvent removable material suchas a photoresist layer or dry film that is removed by an etching processafter exposure to a 150° C. heat treatment for one hour. Alternatively,temporary planarization layer 282 is a water removable material afterexposure to a 150° C. heat treatment for one hour. A first surface oftemporary planarization layer 282 follows a contour of a top surface ofinsulation layer 278, follows a contour of a sidewall of the openings ininsulation layer 278, and is formed over contact pads 277 ofsemiconductor die 276. A second surface of temporary planarization layer282 opposite the first surface is substantially planar and facilitatesthe subsequent mounting of semiconductor die 276 to interface layer 272over carrier 270. Temporary planarization layer 282 provides increasedoffset between the active surface of semiconductor die 276 and a topsurface of interface layer 272.

In FIG. 13 e, printed dots or nodules 280 are formed on interface layer272 and in a periphery of semiconductor die 276 as previously describedin FIG. 13 c. FIG. 13 e further shows semiconductor die 276 is mountedover carrier 270 and interface layer 272 with the active surface of thesemiconductor die oriented towards the carrier and the interface layer.Temporary planarization layer 282 contacts interface layer 272 providingincreased offset between the active surface of semiconductor die 276 anda top surface of interface layer 272, preventing subsequently formedencapsulant from being formed over contact pads 277.

In FIG. 13 f, an optional backside alignment unit 284 is formed over thesurface of carrier 270 and interface layer 272. Backside alignment unit284 contains an alignment key for subsequent laser drilling and marking,or for next level surface mount technology (SMT) alignment. Backsidealignment unit 284 provides alignment when a portion of the backsidealignment unit opposite interface layer 272 is exposed. A plurality ofbackside alignment units 284 are located over portions of carrier 270that facilitate alignment of a plurality of semiconductor die 276 at areconstituted wafer level. Backside alignment units 284 are, forexample, located at four symmetrical positions alternately spaced nearan edge of carrier 270 for global or wafer level alignment. Thealignment of carrier 270 and semiconductor die 276 facilitatessubsequent process steps performed at the reconstituted wafer levelincluding laser drilling, marking, and lithography exposure processes.

In FIG. 13 g, an encapsulant or molding compound 286 is deposited overand around semiconductor die 276, printed dots 280, alignment unit 284,and over interface layer 272 using a paste printing, compressivemolding, transfer molding, liquid encapsulant molding, vacuumlamination, or other suitable applicator. Encapsulant 286 can be polymercomposite material, such as epoxy resin with filler, epoxy acrylate withfiller, or polymer with proper filler. Encapsulant 286 isnon-conductive, provides physical support, and environmentally protectsthe semiconductor device from external elements and contaminants. In oneembodiment, encapsulant 286 has a CTE that is adjusted to match that ofthe base semiconductor material, e.g., Si, with a high Tg in the rangeof 100° C. to 300° C. to reduce warpage. The CTE of encapsulant 286 canbe adjusted using a filler such as a powder, fiber, or cloth additive. Asuitable encapsulant material is generally characterized by good thermalconductivity similar to Si, low-shrinkage, high-resistivity of greaterthan 1.0 kohm-cm, low-dielectric constant of less than 3.5, and low-losstangent of less than 0.02.

Before mounting and encapsulating semiconductor die 276 over carrier270, semiconductor die 276 undergo a back grinding process to thinsemiconductor die 276 to a desired thickness. Alternatively,semiconductor die 276 undergo back grinding at the reconstituted waferlevel after being mounted to carrier 270 and encapsulated withencapsulant 286.

In FIG. 13 h, carrier 270 and interface layer 272 are removed bychemical etching, mechanical peeling, CMP, mechanical grinding, thermalbake, ultra-violet (UV) light, laser scanning, or wet stripping toexpose a bottom surface of encapsulant 286, and a bottom surface oftemporary planarization layer 282 or insulation layer 278. FIG. 13 hfurther shows printed dots 280 are removed to form openings or voids 288in encapsulant 286 located in a periphery of semiconductor die 276,insulation layer 278, and temporary planarization layer 282.Alternatively, in the absence of forming printed dots 280, after theremoval of carrier 270, a portion of encapsulant 286 is removed to formopenings 288. The portion of encapsulant 286 removed to form openings288 is removed by laser drilling or other suitable method. Openings 288are shallow vias or cavities formed in a bottom surface of encapsulant286 in a periphery of semiconductor die 276, insulation layer 278, andtemporary planarization layer 282. Openings 288 extend from the bottomsurface of encapsulant 286 partially but not completely throughencapsulant 286. Openings 288 are configured to receive subsequentlyformed insulation and conductive layers that form a portion of aninterconnect layer that provides electrical connection with respect tosemiconductor die 276.

FIG. 13 i shows openings 288 with sidewalls 290 and bottom portions 292.Sidewalls 290 are tapered rather than vertical as shown in FIG. 13 h.Bottom portions 292 are planar and have an area that is less than anarea of a footprint of a portion of opening 288 that is coplanar withthe bottom surface of encapsulant 286. Tapered sidewalls 290 are formedby laser drilling or other suitable method at the time when openings 288are formed. Alternatively, tapered sidewalls 290 are formed after theinitial formation of openings 288, e.g. after the formation of openings288 with the removal of printed dots 280. As a further alternative,openings 288 are formed with tapered sidewalls upon removal of printeddots 280. FIG. 13 i further shows the formation of openings 294 around aperiphery of semiconductor die 276. Openings 294 are formed by theremoval of encapsulant 286 by laser drilling or other suitable processand provide a smooth contour at the interface between semiconductor die276 and encapsulant 286.

In FIG. 13 j, temporary planarization layer 282 is removed. Temporaryplanarization layer 282 is removed with a wet cleaning process includingsolvent, an aqueous clean with carbon dioxide (CO2) dosing, or othersuitable process. The removal of temporary planarization layer 282exposes insulation layer 278 and portions of contact pads 277 notcovered by insulation layer 278. The removal of temporary planarizationlayer 282, which provided increased offset between the active surface ofsemiconductor die 276 and the top surface of interface layer 272,further provides opening or cavity 296. Opening 296 is formed over theactive surface of semiconductor die 276 and extends from a level of abottom or backside surface of encapsulant 286 to insulation layer 278and contact pads 277 of semiconductor die 276. A surface of opening 296follows a contour of a sidewall of encapsulant 286, extends alonginsulation layer 278, along a sidewall of the openings in insulationlayer 278 over contact pads 277, and along a surface of contact pads277.

In an alternate embodiment, temporary planarization layer 282 is notentirely removed but remains over the active surface of semiconductordie 276 and insulation layer 278 as an additional insulation ordielectric layer. In the embodiment where temporary planarization layer282 is not entirely removed, the temporary planarization layer containsone or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3, hafnium oxide(HfO2), photosensitive polyimide, non-photosensitive polyimide, BCB,PBO, dielectric film material, or other material having similarinsulating and structural properties with a curing temperature of lessthan or equal to 380° C. A portion of temporary planarization layer 282is removed from over contact pads 277 by laser drilling, UV exposure, orother suitable process to form an opening or via which exposes a portionof contact pads 277. The portion of temporary planarization layer 282removed from over contact pads 277 is removed after the curing of thetemporary planarization layer, or alternatively, is removed beforesemiconductor die 276 is singulated and mounted over carrier 270.Furthermore, a portion of insulation layer 278 can also be removed in asame process step as the removal of the portion of temporaryplanarization layer 282 in order to expose the portion of contact pads277.

In FIG. 13 k, a first portion of a FO-WLCSP interconnect or RDL isformed by the deposition and patterning of insulation or passivationlayer 298 and the deposition and patterning of conductive layer 302.Insulation layer 298 is conformally applied to, and has a first surfacethat follows the contours of, encapsulant 286, openings 288 includingsidewalls 290 and bottom surfaces 292, and opening 296. Insulation layer298 has a second planar surface opposite the first surface. Insulationlayer 298 contains one or more layers of photosensitive low curingtemperature dielectric resist, photosensitive composite resist, liquidcrystal polymer (LCP), laminate compound film, insulation paste withfiller, solder mask resist film, liquid molding compound, granularmolding compound, polyimide, BCB, PBO, SiO2, Si3N4, SiON, Ta2O5, Al2O3,or other material having similar insulating and structural properties.Insulation layer 298 is deposited using printing, spin coating, spraycoating, lamination, or other suitable process. Insulation layer 298 issubsequently patterned and cured using UV exposure followed bydeveloping, or other suitable process. A portion of insulation layer 298is removed by laser ablation, etching, or other suitable process toexpose bottom surfaces 292 of openings 288 and contact pads 277 ofsemiconductor die 276 according to the configuration and design ofsemiconductor die 276.

An electrically conductive layer 302 is patterned and deposited overencapsulant 286, semiconductor die 276, and insulation layer 298.Conductive layer 302 can be one or more layers of Al, Cu, Sn, Ni, Au,Ag, or other suitable electrically conductive material. The depositionof conductive layer 302 uses PVD, CVD, electrolytic plating, electrolessplating, or other suitable process. In one embodiment, conductive layer302 includes a seed layer of Ti/Cu, TiW/Cu, or a coupling agent/Cu. Theseed layer is deposited by sputtering, electroless plating, or bydepositing laminated Cu foil combined with electroless plating. In oneembodiment, conductive layer 302 has a thickness of at least 8 um withinthe openings in insulation layer 298. The openings in insulation layer298 extend completely through the insulation layer over openings 288 andover contact pads 277. Conductive layer 302 operates as a RDL to extendelectrical connection from semiconductor die 276 to points external tosemiconductor die 276. A portion of conductive layer 302 formed withinopenings 288 forms lands on the bottom surfaces 292 of openings 288 thatserve as a stop layer for subsequent drilling or removal of a portion ofencapsulant 286 from the top side of encapsulant 286. In one embodiment,the portion of conductive layer 302 formed within openings 288 has awidth that is greater than a width of the portion of conductive layer302 formed over contact pads 277.

In FIG. 13 l, insulation or passivation layer 306 is conformally appliedto, and follows the contours of, insulation layer 298 and conductivelayer 302. Insulation layer 306 contains one or more layers ofphotosensitive low curing temperature dielectric resist, photosensitivecomposite resist, LCP, laminate compound film, insulation paste withfiller, solder mask resist film, liquid molding compound, granularmolding compound, polyimide, BCB, PBO, SiO2, Si3N4, SiON, Ta2O5, Al2O3,or other material having similar insulating and structural properties.Insulation layer 306 is deposited using printing, spin coating, spraycoating, lamination, or other suitable process. Insulation layer 306 issubsequently patterned and cured using UV exposure followed bydeveloping, or other suitable process. A portion of insulation layer 306is removed by laser ablation, etching, or other suitable process toexpose portions of conductive layer 302.

An electrically conductive layer 310 is patterned and deposited overconductive layer 302, insulation layer 306, semiconductor die 276, andencapsulant 286. Conductive layer 310 can be one or more layers of Al,Cu, Sn, Ni, Au, Ag, or other suitable electrically conductive material.The deposition of conductive layer 310 uses PVD, CVD, electrolyticplating, electroless plating, or other suitable process. In oneembodiment, conductive layer 310 includes a seed layer of Ti/Cu, TiW/Cu,or a coupling agent/Cu. The seed layer is deposited by sputtering,electroless plating, or by depositing laminated Cu foil combined withelectroless plating. In one embodiment, conductive layer 310 has athickness of at least 8 um within openings in insulation layer 306. Theopenings in insulation layer 306 extend completely through theinsulation layer over conductive layer 302. Conductive layer 310operates as an RDL to extend electrical connection from semiconductordie 276, through conductive layer 302, to points external tosemiconductor die 276.

In FIG. 13 m, insulation or passivation layer 314 is conformally appliedto, and follows the contours of, insulation layer 306 and conductivelayer 310. Insulation layer 314 contains one or more layers ofphotosensitive low curing temperature dielectric resist, photosensitivecomposite resist, LCP, laminate compound film, insulation paste withfiller, solder mask resist film, liquid molding compound, granularmolding compound, polyimide, BCB, PBO, SiO2, Si3N4, SiON, Ta2O5, Al2O3,or other material having similar insulating and structural properties.Insulation layer 314 is deposited using printing, spin coating, spraycoating, lamination, or other suitable process. Insulation layer 314 issubsequently patterned and cured using UV exposure followed bydeveloping, or other suitable process. A portion of insulation layer 314is removed by laser ablation, etching, or other suitable process toexpose portions of conductive layer 310.

An electrically conductive layer 318 is patterned and deposited overconductive layer 310, insulation layer 314, semiconductor die 276, andencapsulant 286. Conductive layer 318 can be one or more layers of Al,Cu, Sn, Ni, Au, Ag, or other suitable electrically conductive material.The deposition of conductive layer 318 uses PVD, CVD, electrolyticplating, electroless plating, or other suitable process. In oneembodiment, conductive layer 318 includes a seed layer of Ti/Cu, TiW/Cu,or a coupling agent/Cu. The seed layer is deposited by sputtering,electroless plating, or by depositing laminated Cu foil combined withelectroless plating. In one embodiment, conductive layer 318 has athickness of at least 8 um within the openings in insulation layer 314that extend completely through the insulation layer over conductivelayer 310. Conductive layer 318 operates as an RDL to extend electricalconnection from semiconductor die 276, through conductive layers 302 and310, to points external to semiconductor die 276 according to theconfiguration and design of semiconductor die 276. Taken together,insulation layers 298, 306, and 314 as well as conductive layers 302,310, and 318, form interconnect structure 320. The number of insulationand conductive layers included within interconnect 320 depends on, andvaries with, the complexity of circuit routing design. Accordingly,interconnect 320 can include any number of insulation and conductivelayers to facilitate electrical interconnect with respect tosemiconductor die 276. Furthermore, elements that would otherwise beincluded in a backside interconnect structure or RDL can be integratedas part of interconnect 320 to simplify manufacturing and reducefabrication costs with respect to a package including both front sideand backside interconnects or RDLs.

In FIG. 13 n, insulation or passivation layer 322 is conformally appliedto, and follows the contours of, insulation layer 314 and conductivelayer 318. Insulation layer 322 contains one or more layers ofphotosensitive low temperature curing dielectric resist, photosensitivecomposite resist, LCP, laminate compound film, insulation paste withfiller, solder mask resist film, liquid molding compound, granularmolding compound, polyimide, BCB, PBO, SiO2, Si3N4, SiON, Ta2O5, Al2O3,or other material having similar insulating and structural properties.Insulation layer 322 is deposited using printing, spin coating, spraycoating, lamination, or other suitable process. Insulation layer 322 issubsequently patterned and cured with UV exposure followed by developingor other suitable process. A portion of insulation layer 322 is removedby laser ablation, etching, or other suitable process to expose portionsof conductive layer 318.

An electrically conductive bump material is deposited over conductivelayer 318 and insulation layer 322 using an evaporation, electrolyticplating, electroless plating, ball drop, or screen printing process. Thebump material can be Al, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, andcombinations thereof, with an optional flux solution. For example, thebump material can be eutectic Sn/Pb, high-lead solder, or lead-freesolder. The bump material is bonded to conductive layer 318 using asuitable attachment or bonding process. In one embodiment, the bumpmaterial is reflowed by heating the material above its melting point toform spherical balls or bumps 326. In some applications, bumps 326 arereflowed a second time to improve electrical contact to conductive layer318. In one embodiment, bumps 326 are formed over a UBM having a wettinglayer, barrier layer, and adhesive layer. The bumps can also becompression bonded to conductive layer 318. Bumps 326 represent one typeof interconnect structure that can be formed over conductive layer 318.The interconnect structure can also use bond wires, conductive paste,stud bump, micro bump, or other electrical interconnect.

FIGS. 13 o-13 q, similar to FIG. 13 n, show alternate interconnectstructures that can be electrically connected to interconnect 320 forextending electrical connection from semiconductor die 276 to pointsexternal to semiconductor die 276. In FIG. 13 o, instead of bumps 326,bumps 328 are formed over conductive layer 318. Bumps 328 are Ni/Au,Ni/Pt/Au, or Ni/Pd/Au and are formed as I/O pads for extendingelectrical connection from semiconductor die 276 to points external tosemiconductor die 276.

In FIG. 13 p, bumps 332 are formed over conductive layer 318. Bumps 332include plated copper columns and are formed as I/O pads for extendingelectrical connection from semiconductor die 276 to points external tosemiconductor die 276.

In FIG. 13 q, bumps 336 are formed over conductive layer 310. Bumps 336include plated copper and are formed as I/O pads for extendingelectrical connection from semiconductor die 276 to points external tosemiconductor die 276. FIG. 13 q differs from FIGS. 13 n-13 p in that afinal insulation layer 338, similar to insulation layer 322, covers bothconductive layer 310 and bumps 336. Thus, final insulation layer 338 isformed after the formation of bumps 336. In other words, bumps 336 areformed over conductive layer 310 before the formation of insulationlayer 338.

In FIG. 13 r, back grinding tape 342 is applied over semiconductor die276, encapsulant 286, interconnect 320, and bumps 326, 328, 332, or 336.Back grinding tape 342 contacts the final or bottom most layer ofinterconnect 320, such as insulation layer 322, and further contactsfinal I/O pads such as bumps 326. Back grinding tape 342 follows thecontours of a surface of bumps 326 and extends around and between bumps326. Back grinding tape 342 includes tapes with thermal resistance up to270° C. Back grinding tape 342 also includes tapes with a thermalreleasing function. Examples of back grinding tapes 342 include UV tapeHT 440 and non-UV tape MY-595. Back grinding tape 342 providesstructural support for subsequent back grinding and removal of a portionof encapsulant 286 from a backside or top surface of encapsulant 286opposite interconnect 320.

In FIG. 13 r, top surface of encapsulant 286 opposite interconnect 320undergoes a grinding operation with grinder 344 to planarize the surfaceand reduce a thickness of the encapsulant. The grinding operationreduces a thickness of the reconstituted wafer to a thickness in therange of 50 to 600 um. A chemical etch can also be used to remove andplanarize encapsulant 286. After the grinding operation is completed alayer of encapsulant 286 covers a backside surface of semiconductorwafer 276. Alternatively, a backside surface of semiconductor die 276 isexposed from encapsulant 286 after the grinding operation, and athickness of semiconductor die 276 is also reduced by the grindingoperation. In another embodiment, back grinding tape 342 is merelysupporting tape with either a UV or thermal releasing function such thatthe tape, when removed, is removed without a back grinding process.

FIG. 13 s shows an embodiment in which a backside surface ofsemiconductor die 276 is exposed from encapsulant 286 after the grindingoperation. An encapsulant or molding compound 346 is deposited over andcontacts a backside surface of semiconductor die 276 and encapsulant 286using a paste printing, compressive molding, transfer molding, liquidencapsulant molding, vacuum lamination, or other suitable applicator.Encapsulant 346 can be polymer composite material, such as epoxy resinwith filler, epoxy acrylate with filler, or polymer with proper filler.Encapsulant 346 is non-conductive, provides physical support, andenvironmentally protects the semiconductor device from external elementsand contaminants when a need exists to protect the backside ofsemiconductor die 276.

FIG. 13 t, continuing from FIG. 13 r, shows a portion of encapsulant 286is removed from a periphery of semiconductor die 276 and from overconductive layer 302 to form openings 350. Openings 350 include avertical or sloped sidewall and extend from a back surface ofencapsulant 286 completely through the encapsulant to bottom surface 292of opening 288. Openings 350 are formed by drilling, laser ablation,high energy water jetting, etching, or other suitable process to exposeportions of conductive layer 302. In one embodiment, openings 350 serveas round through encapsulant blind vias (TEBVs) that extend to, andcontact, conductive layer 302. Alternatively, openings 350 includecross-sectional profiles of any shape. Openings 350 are formed andsubsequently cleaned while back grinding or supporting tape 342 isattached over interconnect 320 and bumps 326. By forming openings 350 asTEBVs through encapsulant 286 in a periphery of semiconductor die 276, aportion of conductive layer 302 is exposed from a backside ofencapsulant 286. Openings 350 are configured to provide subsequent 3-Delectrical interconnect for semiconductor die 276 without the use ofTSVs or THVs.

FIG. 13 u, similar to FIG. 13 t shows a portion of encapsulant 286 isremoved from a periphery of semiconductor die 276 and over conductivelayer 302 to form openings 352. Openings 352 include sidewalls with afirst portion that is sloped, and second portion that is vertical.Openings 352 extend from a back surface of encapsulant 286 completelythrough the encapsulant to bottom surface 292 of opening 288. Openings352 are formed by drilling, laser ablation, high energy water jetting,etching, or other suitable process to expose portions of conductivelayer 302. Openings 352 serve as TEBVs that extend to and contactconductive layer 302. Openings 352 are formed and subsequently cleanedwhile back grinding or supporting tape 342 is attached over interconnect320 and bumps 326. By forming openings 352 as TEBVs through encapsulant286 in a periphery of semiconductor die 276, a portion of conductivelayer 302 is exposed from a backside of encapsulant 286. Openings 352are configured to provide subsequent 3-D electrical interconnect forsemiconductor die 276 without the use of TSVs or THVs.

In FIG. 13 v, an electrically conductive bump material is deposited inopening 350 and over conductive layer 302 using an evaporation,electrolytic plating, electroless plating, ball drop, screen printing,jetting, or other suitable process. The bump material can be Al, Sn, Ni,Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, with an optionalflux solution. For example, the bump material can be eutectic Sn/Pb,high-lead solder, or lead-free solder. The bump material is bonded toconductive layer 302 using a suitable attachment or bonding process. Inone embodiment, the bump material is reflowed by heating the materialabove its melting point to form spherical balls or bumps 356. In someapplications, bumps 356 are reflowed a second time to improve electricalcontact to conductive layer 302. In one embodiment, bumps 356 are formedover a UBM having a wetting layer, barrier layer, and adhesive layer.The bumps can also be compression bonded to conductive layer 302. Bumps356 represent one type of interconnect structure that can be formed overconductive layer 302. The interconnect structure can also use bondwires, Cu, Ag, or other conductive paste, stud bump, micro bump, solderballs with a Cu core, Cu balls or columns with dipped solder paste orsolder coating, or other electrical interconnect. Bumps 356 form a 3Dinterconnection for next level interconnection. In one embodiment, bumps356 are formed by SMT with paste printing deposited into openings 350 atthe reconstituted wafer level. Accordingly, a 3D interconnection isformed through bumps 356, conductive layer 302, interconnect 320, bumps326, and semiconductor die 276, thereby forming through verticalelectrical interconnection for 3-D FO-WLCSP without a backsideinterconnect or RDL over a footprint of semiconductor die 276.

In FIG. 13 w, back grinding tape 342 is removed after completing thegrinding of encapsulant 286, after the formation and cleaning ofopenings 350, and after the formation of bumps 356. Alternatively, backgrinding tape 342 is removed after completing the grinding ofencapsulant 286 and after the formation and cleaning of openings 350 butbefore the formation of bumps 356. Furthermore, the reconstituted waferis singulated with saw blade or laser cutting device 360 into individual3-D FO-WLCSPs 362. Singulation can occur before or after removal of backgrinding tape 342.

FIG. 13 x shows a 3-D FO-WLCSP 366, similar to 3-D FO-WLCSP 362 fromFIG. 13 w. 3-D FO-WLCSP 366 differs from FO-WLCSP 362 in that 3-DFO-WLCSP 366 was formed without the use of temporary planarization layer282 as shown in FIGS. 13 b and 13 c. Accordingly, the offset ofsemiconductor die 276 with respect to the bottom surface of encapsulant286, and the subsequent presence of opening 296 resulting from theremoval of temporary planarization layer 282, is not present in 3-DFO-WLCSP 366. However, like in FIG. 13 w, the reconstituted wafer issingulated with saw blade or laser cutting device 368 into individual3-D FO-WLCSPs 366. Singulation can occur before or after removal of theback grinding tape.

3-D FO-WLCSPs 362 and 366 provide 3-D electrical interconnection with aninterconnect I/O array through vertical interconnects formed outside afootprint of a semiconductor die without the use of a backside RDLextending within a footprint of the semiconductor die. Optional backsidealignment units with alignment keys are embedded in the encapsulant tofacilitate next level SMT alignment and POP configurations. Laserdrilling or other suitable method is used to form an opening in a frontside of the encapsulant in a periphery of the active surface of thesemiconductor die. An interconnect structure is formed over the activesurface of the semiconductor die and extends into the openings in thefront side of the encapsulant. The interconnect structure includesinsulation and conductive layers that form a FO-WLCSP RDL. Elements thatwould otherwise be included in a backside interconnect structure or RDLcan be integrated as part of a single interconnect structure formed overthe active surface of the semiconductor die. Alternatively, backside RDLelements can be included in other later mounted components of anothersemiconductor device as part of a POP configuration. Bumps or other I/Ointerconnects are formed over the interconnect structure. Backgrindingtape is applied over the bumps, and a portion of the encapsulant and aportion of the backside of the semiconductor die are removed in abackgrinding process. Laser drilling or other suitable process removes aportion of encapsulant in a periphery of the semiconductor die tofacilitate the subsequent formation of vertical interconnects such asround TEBVs that extend from a back surface of the encapsulant to theinterconnect structure. The back grinding tape is removed. A bump orother suitable conductive material is formed in the TEBV to form 3Dvertical interconnects for next level interconnection and POPconfigurations. The reconstituted wafer is singulated.

FIGS. 14 a-14 d, continuing from FIG. 13 t, show another embodiment offorming an electrical connection with conductive layer 302 throughopenings 350. In FIG. 14 a conductive bump material 370 is deposited inopenings 350 at the reconstituted wafer level by printing, jetting, orother suitable process. Conductive bump material 370 is Al, Sn, Ni, Au,Ag, Pb, Bi, Cu, indium (In), solder, and combinations thereof, with anoptional flux solution. For example, conductive bump material 370 can beeutectic Sn/Pb, high-lead solder, or lead-free solder. Conductive bumpmaterial 370 contacts conductive layer 302 and fills a portion ofopenings 350 that is less than an entirety of the openings to facilitatesubsequent electrical interconnect.

In FIG. 14 b, a bumped semiconductor device or package 374 with bumps376 is mounted over 3-D FO-WLCSP 378 at the reconstituted wafer level.Semiconductor device 374 includes interconnect elements that wouldotherwise be included in a backside interconnect structure or RDL formedover the backside of semiconductor 276 that are not included as part ofinterconnect 320. Bumps 376 are Al, Sn, Ni, Au, Ag, Pb, Bi, Cu, In,solder, and combinations thereof, with an optional flux solution. Forexample, bumps 376 can be eutectic Sn/Pb, high-lead solder, or lead-freesolder. Semiconductor device 374 is mounted using pick and place orother suitable operation. Semiconductor device 374 is mounted with bumps376 oriented toward 3-D FO-WLCSP 378 such that bumps 376 extend intoopenings 350 and contact conductive bump material 370 within openings350. The contact between bumps 376 and conductive bump material 370results in an offset 380 between encapsulant 286 and a surface ofsemiconductor device 374. A footprint of semiconductor device 374 has anarea that is larger than an area of a footprint of semiconductor die276. Thus, the footprint of semiconductor die 276 is located within thefootprint of semiconductor device 374 after the semiconductor device hasbeen mounted to 3-D FO-WLCSP 378.

In FIG. 14 c, the reconstituted wafer including semiconductor device 374and 3-D FO-WLCSP 378 are heated to reflow bump material 370 and bumps376. In one embodiment, bump material 370 and bumps 376 are reflowed byheating the materials above their melting points to form spherical ballsor bumps 380. In some applications, bumps 380 are reflowed a second timeto improve electrical contact to conductive layer 302. The bumps canalso be compression bonded to conductive layer 302. Bumps 380 representone type of interconnect structure that can be formed over conductivelayer 302. The interconnect structure can also use bond wires,conductive paste, stud bump, micro bump, or other electricalinterconnect.

In FIG. 14 d, the reconstituted wafer including semiconductor device 374is singulated with saw blade or laser cutting device 384 into individual3-D FO-PoPs 386. FO-PoPs 386 are singulated before back grinding tape342 is removed. Alternatively, back grinding tape 342 is removed aftercompleting the grinding of encapsulant 286 and after the formation andcleaning of openings 350 but before singulation. When back grinding tape342 is removed before singulation of FO-PoPs 386, an optional dicingtape 387 is applied over bumps 326 and contacts insulation layer 322 orthe final or bottom most layer of interconnect 320, follows the contoursof a surface of bumps 326, and extends around and between bumps 326.

FIGS. 15 a-15 d, continuing from FIG. 13 t, show an alternative methodfor forming an electrical connection with conductive layer 302 throughopenings 350. After a portion of encapsulant 286 is removed from overconductive layer 302 to form openings 350, back grinding tape 342 isremoved.

In FIG. 15 b, the reconstituted wafer 388 including semiconductor die276 is aligned and placed on a reusable carrier 390. Carrier 390 is madeof a carrier base material, such as metal, that has thermal conductivityand stiffness properties suitable for minimizing warpage of the carrierin subsequent solder reflow cycles. Carrier 390 includes a plurality ofhalf-ball shaped cavities 392. Cavities 392 are configured to receivebumps 326. Cavities 392 have a height that is less than a height ofbumps 326. In one embodiment, cavities 392 have a height that is atleast 5 um less than a height of bumps 326. Alternatively, cavities 392have a height that is in a range of 5-100 um greater than a height ofbumps 326. The difference in heights between bumps 326 and cavities 392produces a gap or offset 394 between insulation layer 322 and a topsurface of carrier 390. Cavities 392 also have a width that is greaterthan a width of bumps 326. In one embodiment, cavities 392 have a widththat is at least 10 um greater than a width of bumps 326. The differencein widths between bumps 326 and cavities 392 produces a gap or offsetbetween bumps 326 and a contour or surface of cavity 392.

The offset or area between cavities 392 and bumps 326 includes anon-wettable material 396. Non-wettable material 396 is deposited on,and coats, a supporting surface of carrier 390 including a surface ofcavities 392. Non-wettable material 396 includes high temperaturecoatings such as high temperature Teflo, Ti, TiN, or other thin filmmaterials that are inert with respect to bumps 326. Non-wettablematerial 396 is configured to contact bumps 326 at high temperatureswithout reacting or sticking to bumps 326 or insulation layer 322. Forexample, non-wettable material 396 is configured to not react or stickto bumps 326 or insulation layer 322 at temperatures greater than orequal to 280° C.

In one embodiment, carrier 390 includes a vacuum with a vacuum loop orvacuum hole 397 that is configured to maintain reconstituted wafer 388in contact with carrier 390 and non-wettable material 396.

FIG. 15 c, similar to FIG. 15 b, shows reconstituted wafer 388 alignedand placed on reusable carrier 390. FIG. 15 c differs from FIG. 15 b inthat offset 394 between insulation layer 322 and a top surface ofcarrier 390 from FIG. 15 b is replaced with offset 398. Offset 398extends between a surface of bumps 326 and a bottom surface of cavity392, and in one embodiment includes a distance in a range of 5-100 um.

In FIG. 15 d, with reconstituted wafer 388 mounted to reusable carrier390, bumps 400 are deposited or formed within openings 350. Anelectrically conductive bump material is deposited within openings 350and over conductive layer 302 using an evaporation, electrolyticplating, electroless plating, ball drop, or screen printing process. Thebump material can be Al, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, andcombinations thereof, with an optional flux solution. For example, thebump material can be eutectic Sn/Pb, high-lead solder, or lead-freesolder. The bump material is bonded to conductive layer 302 using asuitable attachment or bonding process. In one embodiment, the bumpmaterial is reflowed by heating the material above its melting point toform spherical balls or bumps 400. In some applications, bumps 400 arereflowed a second time to improve electrical contact with conductivelayer 302. The bumps can also be compression bonded to conductive layer302. Bumps 400 represent one type of interconnect structure that can beformed over conductive layer 302. The interconnect structure can alsouse bond wires, conductive paste, stud bump, micro bump, or otherelectrical interconnect.

After the formation of bumps 400, reconstituted wafer 388 is singulatedwith saw blade or laser cutting device 404 into individual 3-D FO-WLCSPs406.

FIGS. 16 a-16 d show an alternative method for forming an electricalconnection with conductive layer 302 through openings 412. FIG. 16 ashows back grinding tape 410, similar to back grinding tape 342 of FIG.13 r, applied over insulation layer 322 before the formation ofconductive bumps similar to bumps or I/O connects 326, 328, 332, and 336from FIGS. 13 n-13 q. Back grinding tape 410 includes tapes with thermalresistance up to 270° C. and tapes with a thermal releasing function.Examples of back grinding tapes 410 include UV tape HT 440 and non-UVtape MY-595. Back grinding tape 410 provides structural support foroptional back grinding of encapsulant 286 at a backside or top surfaceof encapsulant 286 as previously described in FIG. 13 r.

After applying back grinding tape 410, a portion of encapsulant 286 isremoved from over conductive layer 302 to form openings 412. Openings412 include a vertical or sloped sidewall and extend from a back surfaceof encapsulant 286 completely through the encapsulant to bottom surface292 of opening 288. Openings 412 are formed by drilling, laser ablation,high energy water jetting, etching, or other suitable process to exposeportions of conductive layer 302. In one embodiment, openings 412 serveas round TEBVs that extend to, and contact, conductive layer 302.Alternatively, openings 412 include cross-sectional profiles of anyshape. Openings 412 are formed and subsequently cleaned while backgrinding or supporting tape 410 is attached. By forming openings 412 asTEBVs through encapsulant 286 in a periphery of semiconductor die 276, aportion of conductive layer 302 is exposed from a backside ofencapsulant 286.

In FIG. 16 b, back grinding tape 410 is removed after the optionalgrinding of encapsulant 286, and after the formation and cleaning ofopenings 412.

In FIG. 16 c, temporary supporting layer 416 is formed overreconstituted wafer 414. Temporary supporting layer 416 contactsinsulation layer 322 and includes high temperature tape and thermalreleasable tape. Temporary supporting layer 416 supports reconstitutedwafer 414 during the formation and placement of bumps 418 and is removedafter the formation of bumps 418.

Bumps 418 are formed by depositing an electrically conductive bumpmaterial over conductive layer 302 and within openings 412 using anevaporation, electrolytic plating, electroless plating, ball drop,screen printing compression bonding, or other suitable process. The bumpmaterial can be Al, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinationsthereof, with an optional flux solution. For example, the bump materialcan be eutectic Sn/Pb, high-lead solder, or lead-free solder. The bumpmaterial is bonded to conductive layer 302 using a suitable attachmentor bonding process. In one embodiment, the bump material is reflowed byheating the material above its melting point to form spherical balls orbumps 418. In some applications, bumps 418 are reflowed a second time toimprove electrical contact to conductive layer 302. Bumps 418 representone type of interconnect structure that can be formed over conductivelayer 302. The interconnect structure can also use bond wires,conductive paste, stud bump, micro bump, or other electricalinterconnect. Bumps 418 are formed with a height that is less than aheight of opening 412 such that bumps 418 are recessed below a backsideor top surface of encapsulant 286. In one embodiment bumps 418 have aheight at least 1 um less than a height of openings 412.

In another embodiment, temporary supporting layer 416 is optional and isnot applied after the removal of back grinding tape 410. Withouttemporary supporting layer 416 to provide structural support toreconstituted wafer 414 bumps 418 are formed as described above. Whenbumps 418 are formed by a ball drop process a chuck of the ball dropmachine is used to provide temporary support during the placement ofbumps 418. The chuck of the ball drop machine is coated with compliantprotecting material such as Teflo to facilitate the ball drop process.

In FIG. 16 d, temporary supporting layer 422 is formed overreconstituted wafer 414 and contacts a backside surface of encapsulant286. Temporary supporting layer 422 includes high temperature tape,thermal releasable tape, and supports reconstituted wafer 414 during theformation and placement of bumps 424.

Bumps 424 are formed over reconstituted wafer 414, opposite bumps 418,and opposite temporary supporting layer 422. Bumps 424 are formed bydepositing an electrically conductive bump material over conductivelayer 318 using an evaporation, electrolytic plating, electrolessplating, ball drop, or screen printing process. The bump material can beAl, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, withan optional flux solution. For example, the bump material can beeutectic Sn/Pb, high-lead solder, or lead-free solder. The bump materialis bonded to conductive layer 318 using a suitable attachment or bondingprocess. In one embodiment, the bump material is reflowed by heating thematerial above its melting point to form spherical balls or bumps 424.In some applications, bumps 424 are reflowed a second time to improveelectrical contact to conductive layer 318. The bumps can also becompression bonded to conductive layer 318. Bumps 424 represent one typeof interconnect structure that can be formed over conductive layer 318.The interconnect structure can also use bond wires, conductive paste,stud bump, micro bump, or other electrical interconnect.

In another embodiment, temporary supporting layer 422 is optional and isnot applied to reconstituted wafer 414 for the formation of bumps 424.Bumps 424 are formed as described above, but without temporarysupporting layer 422 to provide structural support to reconstitutedwafer 414. When bumps 424 are formed by a ball drop process, a chuck ofthe ball drop machine is used to provide temporary support during theplacement of bumps 424. When used for support, the chuck of the balldrop machine is coated with compliant protecting material such as Teflo.

After the formation of bumps 424, temporary supporting layer 422, ifused, is removed. Reconstituted wafer 414 is singulated with saw bladeor laser cutting device 426 into individual 3-D FO-WLCSPs 428.

FIG. 17 shows 3-D FO-WLCSP 430, similar to 3-D FO-WLCSP 366 from FIG. 13x. 3-D FO-WLCSP 430 differs from FO-WLCSP 366 in that 3-D FO-WLCSP 430is formed without the formation of openings 288 in encapsulant 286.Accordingly, a top surface 432 of conductive layer 434 is planar withtop surface 436 of insulation or passivation layer 438 in a periphery ofsurface 432 rather than including an encapsulant 286 with a steppedconfiguration in a periphery of the conductive layer as shown in FIG. 13x.

FIG. 18 a, similar to FIG. 13 x, shows 3-D FO-WLCSP 442, similar to 3-DFO-WLCSP 366 from FIG. 13 x. 3-D FO-WLCSP 442 differs from FO-WLCSP 366in that 3-D FO-WLCSP 442 is formed with conductive columns 444 andinsulation or passivation layer 446. Conductive columns 444 are formedover front side 448 of encapsulant 450, over contact pads 451 ofsemiconductor die 452, and within openings 453. Conductive columns 444are formed using a patterning and metal deposition process such assputtering, electrolytic plating, and electroless plating. In oneembodiment, conductive columns 444 are Cu. Alternatively, conductivecolumns 444 are one or more layers of Al, Cu, Sn, Ni, Au, Ag, or othersuitable electrically conductive material. In one embodiment, conductivecolumns 444 include a Cu plating seed layer that is deposited with PVDover front side 448 of encapsulant 450, over contact pads 451 ofsemiconductor die 452, and within openings 453. Conductive columns 444are electrically connected to contact pads 451, bumps 454, andinterconnect structure 456.

Insulation layer 446 is formed over encapsulant 450, over semiconductordie 452, and around conductive columns 444, with vacuum lamination,paste printing, compression molding, spin coating, or other suitableprocess. Insulation layer 446 is LCP, laminate compound film, insulationpaste with filler, solder mask resist film, liquid or granular moldingcompound, photosensitive composite resist, and photosensitive low curingtemperature dielectric resist. In one embodiment, insulation layer 446includes an optional dielectric layer that is applied and patterned onfront side 448 of encapsulant 450 after forming opening 453 inencapsulant 450. After the formation of insulation layer 446, theinsulation layer undergoes curing or UV exposure, development, andcuring. After curing, a portion of insulation layer 446 is removed bygrinding, laser drilling, or other suitable process to expose a portionof conductive columns 444 covered by insulation layer 446.

FIG. 18 b shows a 3-D FO-WLCSP 462, similar to the 3-D FO-WLCSP 442 fromFIG. 18 a. 3-D FO-WLCSP 462 differs from FO-WLCSP 442 in that 3-DFO-WLCSP 462 is formed without the formation of openings 453 inencapsulant 450. Accordingly, a top surface 464 of conductive layer 466is planar with front side 468 of encapsulant 450 in a periphery ofsurface 464 rather than including an encapsulant with a steppedconfiguration in a periphery of the conductive layer as shown in FIG. 18a.

FIG. 19 a, similar to FIG. 13 x, includes the additional features ofvias or TSVs 474 and contact pads 476. Vias 474 are formed throughsemiconductor die 478 by deep reactive ion etching (DRIE), laserdrilling, or other suitable process. Vias 474 are filled with Al, Cu,Sn, Ni, Au, Ag, Ti, W, poly-silicon, or other suitable electricallyconductive material using PVD, CVD, electrolytic plating, electrolessplating, or other suitable metal deposition process. Alternatively, aplurality of stud bumps or solder balls can be formed within the vias.Vias 474 extend from contact pads 480 at an active surface ofsemiconductor die 478 to the backside of semiconductor die 478 toprovide through vertical electrical interconnect for 3-D FO-WLCSP 482.

Contact pads or post TSV RDLs 476 are formed over vias 474 and over abackside of semiconductor die 478. Contact pads 476 are made with aconductive material, such as Al, Cu, Sn, Ni, Au, or Ag, and areelectrically connected to vias 474 and contact pads 480. Contact pads476 are formed by PVD, CVD, electrolytic plating, electroless plating,or other suitable process. Contact pads 476 are exposed when a backsideor top surface of encapsulant 484 over contact pads 476 undergoes agrinding operation to planarize the surface and reduce a thickness ofthe encapsulant. In one embodiment, contact pads 476 are exposed by theback grinding process before the formation of openings 486.Alternatively, contact pads 476 can be exposed with shallow laserdrilling or other suitable process either before or after the formationof openings 486.

FIG. 19 b shows 3-D FO-WLCSP 490 similar to 3-D FO-WLCSP 482 from FIG.19 a. 3-D FO-WLCSP 490 differs from FO-WLCSP 482 with the inclusion ofsemiconductor die 492 mounted with microbumps 494 over a backside ofsemiconductor die 496. Semiconductor die 492 is mounted at a panellevel, at the reconstituted wafer level, or alternatively after an SMTprocess.

FIG. 20 a shows a 3-D FO-WLCSP 500 similar to 3-D FO-WLCSP 366 from FIG.13 x. In FIG. 20 a, a backside surface of semiconductor die 502 isexposed from encapsulant 504. An encapsulant or molding compound 506 isdeposited over and contacts an entire backside or top surface ofsemiconductor die 502 and encapsulant 504. Encapsulant 506 is depositedusing vacuum lamination, paste printing, compression molding, transfermolding, liquid encapsulant molding, spin coating, spray coating orother suitable process followed by curing. Encapsulant 506 is LCP withor without Cu foil, laminate compound film, insulation paste withfiller, solder mask resist film, liquid or granular molding compound,photosensitive composite resist, photosensitive low curing temperaturedielectric resist, or other suitable material. Encapsulant 506 isnon-conductive, provides physical support, and environmentally protectsthe semiconductor device from external elements and contaminants. In oneembodiment, encapsulant 506 has a CTE equal to or greater than 15 ppmand is black in color. A thickness of encapsulant 506 and other materialproperties of encapsulant 506 are selected to obtain desired warpage andreliability performance for 3-D FO-WLCSP 500.

FIG. 20 b shows 3-D FO-WLCSP 510 similar to 3-D FO-WLCSP 500 from toFIG. 20 a. Rather than depositing encapsulant or molding compound 506over an entire backside or top surface of semiconductor die 502 andencapsulant 504, encapsulant 512 is deposited over a backside surface ofsemiconductor die 514 and a portion of encapsulant 516. However,encapsulant 512 is not formed in a periphery of openings 518.Encapsulant 512 provides physical support and environmentally protectssemiconductor die 514 from external elements and contaminants. In oneembodiment, encapsulant 512 has a CTE equal to or greater than 15 ppmand is black in color. A thickness of encapsulant 512 and other materialproperties of the encapsulant are selected to obtain desired warpage andreliability performance for 3-D FO-WLCSP 510.

FIG. 21 a shows 3-D FO-WLCSP 522 similar to 3-D FO-WLCSP 366 from FIG.13 x. FO-WLCSP 522 differs from FO-WLCSP 366 in that encapsulant 524 isformed with a stepped portion 526 of encapsulant 524 that has a verticaloffset 528 from a back surface of encapsulant 524 outside a footprint ofsemiconductor die 530. Thus stepped portion 526 forms a stepped mold capthat protrudes over a backside of semiconductor die 530. Stepped portion526 is formed during formation of encapsulant 524. Alternatively,stepped portion 526 is formed in a selective back grinding process.Stepped portion 526 has a thickness 532 over a backside of semiconductordie 530, and in one embodiment thickness 532 is less than a thickness ofsemiconductor die 530. In another embodiment, thickness 532 is greaterthan or equal to a thickness of semiconductor die 530. Thickness 532,vertical offset 528, and a length and width of a stepped portion 526 areadjusted in order to optimize package aspect ratios and the performanceof 3-D FO-WLCSP 522 in terms of thermal performance, and warpage. Thelength and width of stepped portion 526 are adjusted according to thedesign of 3-D FO-WLCSP 522 to form an area that is larger than afootprint of semiconductor die 530. Alternatively, the length and widthof stepped portion 526 are adjusted to form an area that is smaller thanor equal to a footprint of semiconductor die 530. In one embodiment, anouter edge of stepped portion 526 is vertically aligned with an outeredge of semiconductor die 530.

FIG. 21 b shows 3-D FO-WLCSP 538 similar to the 3-D FO-WLCSP 522 fromFIG. 21 a. Encapsulant 540 has a vertical offset 542 with respect to aback surface of encapsulant 540 outside a footprint of semiconductor die544. Thus, vertical offset 542 forms a stepped mold cap that protrudesover a backside of semiconductor die 544. Vertical offset 542 is formedduring formation of encapsulant 540. Alternatively, vertical offset 542is formed in a selective back grinding process. A semiconductor deviceor package 546 is mounted over semiconductor die 544 and is electricallyconnected to conductive layer 548 with bumps 550. A bottom surface ofsemiconductor device 546 has a vertical offset 552 with respect to aback surface of encapsulant 540 outside a footprint of semiconductor544. A distance of vertical offset 552 is greater than a distance ofvertical offset 542 such that the bottom surface of semiconductor device546 does not contact a back surface of encapsulant 540, including a backsurface of the stepped mold cap.

FIG. 21 c shows 3-D FO-WLCSP 556 similar to 3-D FO-WLCSP 538 from FIG.21 b. Encapsulant 558 has a vertical offset 560 with respect to a top orbackside surface of encapsulant 558 that forms a cavity 561 in theencapsulant over a backside of semiconductor die 562. Vertical offset560 forms cavity 561 that is recessed with respect to, and is lowerthan, the top or backside surface of encapsulant 558 outside a footprintof the cavity. Cavity 561 is formed during formation of encapsulant 558.Alternatively, cavity 561 is formed in a selective back grindingprocess, by shallow laser grooving, wet etching, or other suitablemethod. Cavity 561 is configured to provide space for a later mountedsemiconductor device such as a flip chip semiconductor device, bond wireBGA, bond wire LGA, discrete component, or other semiconductor device.

A semiconductor device or package 564 is mounted over semiconductor die562 and is electrically connected to conductive layer 566 with bumps568. A bottom surface of semiconductor device 564 has a vertical offset570 with respect to a top or backside surface of encapsulant 558. Asemiconductor device or package 572 is mounted to semiconductor device564 and is between bumps 568. A combined distance of vertical offset 560and 570 is greater than a vertical distance occupied by semiconductordevice 572. Accordingly, semiconductor device 572 fits within cavity 561and is positioned over and does not contact encapsulant 558.

FIG. 22 a shows 3-D FO-WLCSP 576 similar to 3-D FO-WLCSP 366 from FIG.13 x. However, FO-WLCSP 576 does not include the formation of electricalinterconnects or bumps similar to bumps 536 in FO-WLCSP 366 for top sideelectrical interconnection. Electrical interconnects within openings 578are not formed prior to completion of 3-D FO-WLCSP 576. Instead, anelectrical interconnect is formed in openings 578 during an SMT processfor next level interconnection, or as part of a PoP assembly process,after completion of 3-D FO-WLCSP 576.

FIG. 22 b, similar to FIG. 22 a, shows another embodiment in whichelectrical interconnects or bumps similar to bumps 356 in FO-WLCSP 366are not formed until after completion of 3-D FO-WLCSP 580. Electricalinterconnects are formed in openings 582 during an SMT process for nextlevel interconnection, or as part of a PoP assembly process. In contrastwith FIG. 22 a, FIG. 22 b shows a backside of semiconductor die 584 isexposed from encapsulant 586 as part of singulated 3-D FO-WLCSP 580.

FIG. 22 c, similar to FIG. 22 b, shows FO-WLCSP 590 with conductivelayer 592 formed over, or on, a top or backside surface of encapsulant594 and over a backside of semiconductor die 596. Conductive layer orfilm 592 is Cu, Al, ferrite or carbonyl iron, stainless steel, nickelsilver, low-carbon steel, silicon-iron steel, foil, conductive resin,and other material with high thermal conductivity or capable of blockingor absorbing electromagnetic interference (EMI), radio frequencyinterference (RFI), harmonic distortion, and other inter-deviceinterference. Conductive layer 592 is patterned and conformallydeposited using a lamination, printing, electrolytic plating,electroless plating, sputtering, PVD, CVD, or other suitable metaldeposition process. Conductive layer 592 can be formed with an optionalinsulation or protection layer 596.

Optional insulation layer 596 is formed over a backside of semiconductordie 596. Insulation layer 596 contains one or more layers ofphotosensitive low curing temperature dielectric resist, photosensitivecomposite resist, LCP, laminate compound film, insulation paste withfiller, solder mask resist film, liquid molding compound, granularmolding compound, polyimide, BCB, PBO, SiO2, Si3N4, SiON, Ta2O5, Al2O3,or other material having similar insulating and structural properties.Insulation layer 596 is deposited using printing, spin coating, spraycoating, lamination, or other suitable process.

Conductive layer 592 and optional insulation layer 596 can be formed onthe backside of encapsulant 594 and semiconductor die 596 before orafter the formation of openings 598. In one embodiment, conductive layer592 acts as a heat sink to improve thermal performance of 3-D FO-WLCSP590. In another embodiment, conductive layer 592 acts as a shieldinglayer for blocking or absorbing EMI, RFI, harmonic distortion, and otherinterference.

FIG. 23 shows a 3-D FO-WLCSP 600, similar to 3-D FO-WLCSP 362 from FIG.13 w. 3-D FO-WLCSP 600 differs from FO-WLCSP 362 by the inclusion ofcrack stop layer 602. Crack stop layer 602 is conformally applied over,and follows the contours of, insulation layer 604 over semiconductor die606 with spin coating, vacuum lamination, screen printing, or othersuitable process. Crack stop layer 602 contains one or more layers ofSiO2, Si3N4, SiON, Ta2O5, Al2O3, HfO2, photosensitive polyimide,non-photosensitive polyimide, BCB, PBO, dielectric film material, orother material having similar insulating and structural properties witha curing temperature of less than or equal to 380° C. Crack stop layer602 has a high tensile strength and high elongation that aids in theprevention of cracks within 3-D FO-WLCSP 600. In one embodiment, crackstop layer 602 has a tensile strength greater than or equal to 100megapascals (MPa) and an elongation in the range of 30-150%. A portionof crack stop layer 602 is removed from over contact pads 277 by laserdrilling, reactive ion etching (RIE), UV exposure, or other suitableprocess to form an opening or via which exposes a portion of contactpads 277. The portion of crack stop layer 602 removed from over contactpads 277 is removed after the curing of the crack stop layer, oralternatively, is removed before semiconductor die 606 is singulated andsubsequently mounted within a portion of 3-D FO-WLCSP 600. In oneembodiment, a portion of insulation layer 604 is also removed in a sameprocess step as the removal of the portion of crack stop layer 602 inorder to expose the portion of contact pads 277.

FIG. 24 a shows a 3-D FO-WLCSP 610, similar to 3-D FO-WLCSP 362 fromFIG. 13 w. 3-D FO-WLCSP 610 differs from FO-WLCSP 362 by inclusion of aninterconnect structure 612 that is expanded horizontally with respect tointerconnect 320. Interconnect structure 612 includes conductive layer614, similar to conductive layer 302, that extends into openings orvoids 616 and 618 in encapsulant 620. Openings 616 and 618 are analogousto openings 288 in FIG. 13 h, and are formed in a front side ofencapsulant 620. Openings 624 are analogous to openings 350 from FIG. 13t, and are formed in a backside of encapsulant 620 and over openings616. Openings 624 are not formed over openings 618. Accordingly, notevery opening 616 and 618 formed in the front side of encapsulant 620will have a corresponding opening 624 formed in the backside ofencapsulant 620. Openings 618 that do not have a corresponding opening624 formed in the backside of encapsulant 620 are positioned within 3-DFO-WLCSP 610 such that bump or front side I/O interconnects 628 areformed over, and vertically aligned with, openings 618. The number andconfiguration of conductive and insulation or passivation layersincluded within interconnect structure 612 varies with the complexity ofcircuit routing design according to the design and function of 3-DFO-WLCSP 610, and provides additional interconnect capabilites.

FIG. 24 b, similar to FIG. 24 a, shows FO-WLCSP 632 with a horizontallyexpanded interconnect structure 634 that extends into openings 636, 638,and 640. Conductive layer 642 is conformally applied to, and follows thecontours of, insulation or passivation layer 644. Conductive layer 642extends into openings 636, but does not extend into openings 638 and640. Opening 638 does not have a corresponding opening 644 formed in thebackside of encapsulant 646, and is positioned within 3-D FO-WLCSP 632such that a bump or front side I/O interconnect 648 is formed over, andis vertically aligned with, opening 638. A portion of conductive layer642, while not extending into opening 638, does extend between opening638 and interconnect 648. Similarly, opening 640 does not have acorresponding opening 644 formed in the backside of encapsulant 646, butis positioned within 3-D FO-WLCSP 632 such that a bump or front side I/Ointerconnect 648 is formed over, and is horizontally aligned with,opening 640. A portion of conductive layer 642 does not extend betweenopening 640 and interconnect 648. The number and configuration ofconductive and insulation or passivation layers within interconnect 634varies with the complexity of circuit routing design according to thedesign and function of 3-D FO-WLCSP 632.

FIG. 25 a, similar to FIG. 24 a, shows 3-D FO-WLCSP 652 with ahorizontally expanded interconnect structure 654. 3-D FO-WLCSP 652includes encapsulant layer 656 with openings or voids 658 formed inmultiple rows on a front side of the encapsulant layer. Interconnectstructure 654 is formed over the front side of encapsulant 654 and aportion of the interconnect structure extends into openings 658.Conductive layer 660 is formed as a portion of interconnect structure654 and is conformally applied to, and follows the contours of,insulation or passivation layer 662. Conductive layer 660 extends intoopenings 658, and each opening 658 has a corresponding opening 664formed in the backside of encapsulant 656. Accordingly, openings 664 areformed in multiple rows and are positioned as an array for verticalelectrical connection through the backside of FO-WLCSP 652. Electricalconnection through openings 664 is accomplished by depositing conductivematerial within the openings and on interconnect structure 654 aspreviously described. Openings 658 are positioned within 3-D FO-WLCSP652 such that a bump or front side I/O interconnect 668 is formed over,and is vertically aligned with, each opening 658. The number andconfiguration of conductive and insulation or passivation layers withininterconnect 654 varies with the complexity of circuit routing designand according to the design and function of 3-D FO-WLCSP 652.Accordingly, 3-D FO-WLCSP 652 provides 3-D electrical interconnectionwith an interconnect I/O array through vertical interconnects formedoutside a footprint of semiconductor die 670 without the use of abackside RDL that extends within a footprint of the semiconductor die.

FIG. 25 b, similar to FIG. 25 a, shows 3-D FO-WLCSP 674 with ahorizontally expanded interconnect structure 676. 3-D FO-WLCSP 674differs from FO-WLCSP 652 in that a thin layer of insulation orpassivation 678 remains in opening 680 between opening 684 formed in abackside of encapsulant 682 and conductive layer 686. In one embodimentinsulation layer 678 is underdeveloped such that the thin layer ofinsulation layer 678 remains in opening 680. Accordingly, 3-D FO-WLCSP674 provides 3-D electrical interconnection with an interconnect I/Oarray through vertical interconnects formed outside a footprint ofsemiconductor die 686 without the use of a backside RDL that extendswithin a footprint of the semiconductor die.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

What is claimed:
 1. A semiconductor device, comprising: a semiconductordie; an encapsulant deposited over a periphery of the semiconductor dieincluding a stepped portion of the encapsulant extending across asurface of the semiconductor die; an interconnect structure formed overthe semiconductor die opposite the stepped portion of the encapsulant;and a via formed in the encapsulant extending from a first surface ofthe encapsulant to the interconnect structure.
 2. The semiconductordevice of claim 1, wherein the via that extends from the first surfaceof the encapsulant to the interconnect structure includes a sidewallwith a vertical or tapered profile.
 3. The semiconductor device of claim1, further including a crack stop layer deposited over the semiconductordie.
 4. The semiconductor device of claim 1, further including abackside alignment unit disposed in the periphery of the semiconductordie.
 5. The semiconductor device of claim 1, further including aplurality of conductive vias that extend from the first surface of theencapsulant to a second surface of the encapsulant and organized as anarray with multiple rows.
 6. A semiconductor device, comprising: asemiconductor die; an insulating layer formed over a surface of thesemiconductor die; a preventative layer extending across the insulatinglayer over the semiconductor die to reduce formation of cracks with theinsulating layer between the semiconductor die and the preventativelayer; and an interconnect structure formed over the semiconductor die.7. The semiconductor device of claim 6, further including a conductivematerial disposed over a periphery of the semiconductor die.
 8. Thesemiconductor device of claim 6, further including an encapsulantdeposited over the semiconductor die wherein a surface of theencapsulant includes a step with a vertical offset.
 9. The semiconductordevice of claim 6, further including a temporary planarization andprotection layer deposited over the surface of the semiconductor die.10. The semiconductor device of claim 6, further including back grindingtape deposited over the interconnect structure.
 11. A semiconductordevice, comprising: a semiconductor die; an encapsulant disposed overthe semiconductor die; a bump disposed within a via of the encapsulantover a periphery of the semiconductor die; a conductive pillar disposedover the bump; and an interconnect structure formed over thesemiconductor die.
 12. The semiconductor device of claim 11, wherein theinterconnect structure includes a solder bump.
 13. The semiconductordevice of claim 11, further including back grinding tape deposited overthe interconnect structure.
 14. A semiconductor device, comprising: asemiconductor die; a first conductive layer disposed over thesemiconductor die including a first portion of the first conductivelayer isolated from a second portion of the first conductive layer; andan interconnect structure coupled to the first conductive layer anddisposed between the first and second portions of the first conductivelayer.
 15. The semiconductor device of claim 14, wherein theinterconnect structure includes a solder bump disposed over the firstconductive layer.
 16. The semiconductor device of claim 14, furtherincluding an encapsulant disposed around the semiconductor die.
 17. Thesemiconductor device of claim 14, further including a temporaryplanarization and protection layer deposited over a surface of thesemiconductor die.
 18. The semiconductor device of claim 14, furtherincluding back grinding tape deposited over the interconnect structure.19. The semiconductor device of claim 1, wherein the encapsulant hasundergone a back grinding operation to reduce a thickness of thesemiconductor device.
 20. The semiconductor device of claim 1, whereinthe semiconductor die includes a pre-applied adhesive disposed over thesemiconductor die.